diff --git a/telebot/__init__.py b/telebot/__init__.py
index ca93487..5fed5c1 100644
--- a/telebot/__init__.py
+++ b/telebot/__init__.py
@@ -252,7 +252,7 @@ class TeleBot:
         """
 
         self.current_states = StateFile(filename=filename)
-        self.current_states._create_dir()
+        self.current_states.create_dir()
 
     def enable_save_reply_handlers(self, delay=120, filename="./.handler-saves/reply.save"):
         """
@@ -1221,11 +1221,13 @@ class TeleBot:
                 reply_to_message_id = reply_to_message_id, reply_markup = reply_markup, parse_mode = parse_mode,
                 disable_notification = disable_notification, timeout = timeout, caption = caption, thumb = thumb,
                 caption_entities = caption_entities, allow_sending_without_reply = allow_sending_without_reply,
-                disable_content_type_detection = disable_content_type_detection, visible_file_name = visible_file_name, protect_content = protect_content))
+                disable_content_type_detection = disable_content_type_detection, visible_file_name = visible_file_name,
+                protect_content = protect_content))
 
     # TODO: Rewrite this method like in API.
     def send_sticker(
-            self, chat_id: Union[int, str], sticker: Union[Any, str], 
+            self, chat_id: Union[int, str],
+            sticker: Union[Any, str],
             reply_to_message_id: Optional[int]=None, 
             reply_markup: Optional[REPLY_MARKUP_TYPES]=None,
             disable_notification: Optional[bool]=None, 
@@ -1236,6 +1238,7 @@ class TeleBot:
         """
         Use this method to send .webp stickers.
         :param chat_id:
+        :param sticker:
         :param data:
         :param reply_to_message_id:
         :param reply_markup:
@@ -1254,7 +1257,8 @@ class TeleBot:
                 self.token, chat_id, sticker, 'sticker',
                 reply_to_message_id=reply_to_message_id, reply_markup=reply_markup,
                 disable_notification=disable_notification, timeout=timeout, 
-                allow_sending_without_reply=allow_sending_without_reply, protect_content=protect_content))
+                allow_sending_without_reply=allow_sending_without_reply,
+                protect_content=protect_content))
 
     def send_video(
             self, chat_id: Union[int, str], video: Union[Any, str], 
@@ -1330,6 +1334,7 @@ class TeleBot:
         :param thumb: InputFile or String : Thumbnail of the file sent
         :param caption: String : Animation caption (may also be used when resending animation by file_id).
         :param parse_mode:
+        :param protect_content:
         :param reply_to_message_id:
         :param reply_markup:
         :param disable_notification:
@@ -1924,7 +1929,7 @@ class TeleBot:
         return apihelper.set_my_commands(self.token, commands, scope, language_code)
     
     def delete_my_commands(self, scope: Optional[types.BotCommandScope]=None, 
-            language_code: Optional[int]=None) -> bool:
+            language_code: Optional[str]=None) -> bool:
         """
         Use this method to delete the list of the bot's commands for the given scope and user language. 
         After deletion, higher level commands will be shown to affected users. 
@@ -2559,7 +2564,7 @@ class TeleBot:
         :param chat_id:
         """
         for key, value in kwargs.items():
-            self.current_states._add_data(chat_id, key, value)
+            self.current_states.add_data(chat_id, key, value)
 
     def register_next_step_handler_by_chat_id(
             self, chat_id: Union[int, str], callback: Callable, *args, **kwargs) -> None:
diff --git a/telebot/apihelper.py b/telebot/apihelper.py
index 3f9562d..870c609 100644
--- a/telebot/apihelper.py
+++ b/telebot/apihelper.py
@@ -144,6 +144,7 @@ def _make_request(token, method_name, method='get', params=None, files=None):
             method, request_url, params=params, files=files,
             timeout=(connect_timeout, read_timeout), proxies=proxy)
     elif CUSTOM_REQUEST_SENDER:
+        # noinspection PyCallingNonCallable
         result = CUSTOM_REQUEST_SENDER(
             method, request_url, params=params, files=files,
             timeout=(connect_timeout, read_timeout), proxies=proxy)
@@ -246,6 +247,7 @@ def send_message(
     :param timeout:
     :param entities:
     :param allow_sending_without_reply:
+    :param protect_content:
     :return:
     """
     method_url = r'sendMessage'
@@ -861,7 +863,8 @@ def send_audio(token, chat_id, audio, caption=None, duration=None, performer=Non
 
 def send_data(token, chat_id, data, data_type, reply_to_message_id=None, reply_markup=None, parse_mode=None,
               disable_notification=None, timeout=None, caption=None, thumb=None, caption_entities=None,
-              allow_sending_without_reply=None, disable_content_type_detection=None, visible_file_name=None):
+              allow_sending_without_reply=None, disable_content_type_detection=None, visible_file_name=None,
+              protect_content = None):
     method_url = get_method_by_type(data_type)
     payload = {'chat_id': chat_id}
     files = None
@@ -896,6 +899,8 @@ def send_data(token, chat_id, data, data_type, reply_to_message_id=None, reply_m
         payload['caption_entities'] = json.dumps(types.MessageEntity.to_list_of_dicts(caption_entities))
     if allow_sending_without_reply is not None:
         payload['allow_sending_without_reply'] = allow_sending_without_reply
+    if protect_content is not None:
+        payload['protect_content'] = protect_content
     if method_url == 'sendDocument' and disable_content_type_detection is not None:
         payload['disable_content_type_detection'] = disable_content_type_detection
     return _make_request(token, method_url, params=payload, files=files, method='post')
@@ -1382,6 +1387,7 @@ def send_invoice(
     :param max_tip_amount: The maximum accepted amount for tips in the smallest units of the currency
     :param suggested_tip_amounts: A JSON-serialized array of suggested amounts of tips in the smallest units of the currency.
         At most 4 suggested tip amounts can be specified. The suggested tip amounts must be positive, passed in a strictly increased order and must not exceed max_tip_amount.
+    :param protect_content:
     :return:
     """
     method_url = r'sendInvoice'
diff --git a/telebot/async_telebot.py b/telebot/async_telebot.py
index 011ff46..0e1deae 100644
--- a/telebot/async_telebot.py
+++ b/telebot/async_telebot.py
@@ -1335,7 +1335,7 @@ class AsyncTeleBot:
         """
 
         self.current_states = asyncio_handler_backends.StateFile(filename=filename)
-        self.current_states._create_dir()
+        self.current_states.create_dir()
 
     async def set_webhook(self, url=None, certificate=None, max_connections=None, allowed_updates=None, ip_address=None,
                     drop_pending_updates = None, timeout=None):
@@ -1790,6 +1790,7 @@ class AsyncTeleBot:
         :param timeout: timeout
         :param allow_sending_without_reply:
         :param protect_content:
+        :param data: deprecated, for backward compatibility
         :return: API reply.
         """
         if data and not(sticker):
@@ -1837,13 +1838,16 @@ class AsyncTeleBot:
         :param allow_sending_without_reply:
         :param reply_markup:
         :param timeout:
-        :param data: function typo miss compatibility: do not use it
+        :param data: deprecated, for backward compatibility
         """
         parse_mode = self.parse_mode if (parse_mode is None) else parse_mode
+        if data and not(video):
+            # function typo miss compatibility
+            video = data
 
         return types.Message.de_json(
             await asyncio_helper.send_video(
-                self.token, chat_id, data, duration, caption, reply_to_message_id, reply_markup,
+                self.token, chat_id, video, duration, caption, reply_to_message_id, reply_markup,
                 parse_mode, supports_streaming, disable_notification, timeout, thumb, width, height,
                 caption_entities, allow_sending_without_reply, protect_content))
 
@@ -1873,6 +1877,7 @@ class AsyncTeleBot:
         :param thumb: InputFile or String : Thumbnail of the file sent
         :param caption: String : Animation caption (may also be used when resending animation by file_id).
         :param parse_mode:
+        :param protect_content:
         :param reply_to_message_id:
         :param reply_markup:
         :param disable_notification:
@@ -3057,4 +3062,4 @@ class AsyncTeleBot:
         :param chat_id:
         """
         for key, value in kwargs.items():
-            await self.current_states._add_data(chat_id, key, value)
\ No newline at end of file
+            await self.current_states.add_data(chat_id, key, value)
diff --git a/telebot/asyncio_handler_backends.py b/telebot/asyncio_handler_backends.py
index d3c452f..0a78a90 100644
--- a/telebot/asyncio_handler_backends.py
+++ b/telebot/asyncio_handler_backends.py
@@ -28,7 +28,7 @@ class StateMemory:
         """Delete a state"""
         self._states.pop(chat_id)
 
-    def _get_data(self, chat_id):
+    def get_data(self, chat_id):
         return self._states[chat_id]['data']
 
     async def set(self, chat_id, new_state):
@@ -39,7 +39,7 @@ class StateMemory:
         """
         await self.add_state(chat_id,new_state)
 
-    async def _add_data(self, chat_id, key, value):
+    async def add_data(self, chat_id, key, value):
         result = self._states[chat_id]['data'][key] = value
         return result
 
@@ -77,28 +77,28 @@ class StateFile:
         :param chat_id:
         :param state: new state
         """
-        states_data = self._read_data()
+        states_data = self.read_data()
         if chat_id in states_data:
             states_data[chat_id]['state'] = state
-            return await self._save_data(states_data)
+            return await self.save_data(states_data)
         else:
-            new_data = states_data[chat_id] = {'state': state,'data': {}}
-            return await self._save_data(states_data)
+            states_data[chat_id] = {'state': state,'data': {}}
+            return await self.save_data(states_data)
 
 
     async def current_state(self, chat_id):
         """Current state."""
-        states_data = self._read_data()
+        states_data = self.read_data()
         if chat_id in states_data: return states_data[chat_id]['state']
         else: return False
 
     async def delete_state(self, chat_id):
         """Delete a state"""
-        states_data = self._read_data()
+        states_data = self.read_data()
         states_data.pop(chat_id)
-        await self._save_data(states_data)
+        await self.save_data(states_data)
 
-    def _read_data(self):
+    def read_data(self):
         """
         Read the data from file.
         """
@@ -107,7 +107,7 @@ class StateFile:
         file.close()
         return states_data
 
-    def _create_dir(self):
+    def create_dir(self):
         """
         Create directory .save-handlers.
         """
@@ -117,7 +117,7 @@ class StateFile:
             with open(self.file_path,'wb') as file:
                 pickle.dump({}, file)
         
-    async def _save_data(self, new_data):
+    async def save_data(self, new_data):
         """
         Save data after editing.
         :param new_data:
@@ -126,8 +126,8 @@ class StateFile:
             pickle.dump(new_data, state_file, protocol=pickle.HIGHEST_PROTOCOL)
         return True
 
-    def _get_data(self, chat_id):
-        return self._read_data()[chat_id]['data']
+    def get_data(self, chat_id):
+        return self.read_data()[chat_id]['data']
 
     async def set(self, chat_id, new_state):
         """
@@ -138,10 +138,10 @@ class StateFile:
         """
         await self.add_state(chat_id,new_state)
 
-    async def _add_data(self, chat_id, key, value):
-        states_data = self._read_data()
+    async def add_data(self, chat_id, key, value):
+        states_data = self.read_data()
         result = states_data[chat_id]['data'][key] = value
-        await self._save_data(result)
+        await self.save_data(result)
 
         return result
 
@@ -173,7 +173,7 @@ class StateContext:
     def __init__(self , obj: StateMemory, chat_id) -> None:
         self.obj = obj
         self.chat_id = chat_id
-        self.data = obj._get_data(chat_id)
+        self.data = obj.get_data(chat_id)
 
     async def __aenter__(self):
         return self.data
@@ -191,14 +191,14 @@ class StateFileContext:
         self.data = None
 
     async def __aenter__(self):
-        self.data = self.obj._get_data(self.chat_id)
+        self.data = self.obj.get_data(self.chat_id)
         return self.data
 
     async def __aexit__(self, exc_type, exc_val, exc_tb):
-        old_data = self.obj._read_data()
+        old_data = self.obj.read_data()
         for i in self.data:
             old_data[self.chat_id]['data'][i] = self.data.get(i)
-        await self.obj._save_data(old_data)
+        await self.obj.save_data(old_data)
 
         return
 
diff --git a/telebot/asyncio_helper.py b/telebot/asyncio_helper.py
index fc02775..e36a974 100644
--- a/telebot/asyncio_helper.py
+++ b/telebot/asyncio_helper.py
@@ -1,8 +1,6 @@
 import asyncio # for future uses
-from time import time
 import aiohttp
 from telebot import types
-import json
 
 try:
     import ujson as json
@@ -853,6 +851,8 @@ async def send_data(token, chat_id, data, data_type, reply_to_message_id=None, r
         payload['caption_entities'] = json.dumps(types.MessageEntity.to_list_of_dicts(caption_entities))
     if allow_sending_without_reply is not None:
         payload['allow_sending_without_reply'] = allow_sending_without_reply
+    if protect_content is not None:
+        payload['protect_content'] = protect_content
     if method_url == 'sendDocument' and disable_content_type_detection is not None:
         payload['disable_content_type_detection'] = disable_content_type_detection
     return await _process_request(token, method_url, params=payload, files=files, method='post')
diff --git a/telebot/handler_backends.py b/telebot/handler_backends.py
index 45b903b..1e67870 100644
--- a/telebot/handler_backends.py
+++ b/telebot/handler_backends.py
@@ -168,7 +168,7 @@ class StateMemory:
         """Delete a state"""
         self._states.pop(chat_id)
 
-    def _get_data(self, chat_id):
+    def get_data(self, chat_id):
         return self._states[chat_id]['data']
 
     def set(self, chat_id, new_state):
@@ -179,7 +179,7 @@ class StateMemory:
         """
         self.add_state(chat_id,new_state)
 
-    def _add_data(self, chat_id, key, value):
+    def add_data(self, chat_id, key, value):
         result = self._states[chat_id]['data'][key] = value
         return result
 
@@ -217,28 +217,27 @@ class StateFile:
         :param chat_id:
         :param state: new state
         """
-        states_data = self._read_data()
+        states_data = self.read_data()
         if chat_id in states_data:
             states_data[chat_id]['state'] = state
-            return self._save_data(states_data)
+            return self.save_data(states_data)
         else:
-            new_data = states_data[chat_id] = {'state': state,'data': {}}
-            return self._save_data(states_data)
-
+            states_data[chat_id] = {'state': state,'data': {}}
+            return self.save_data(states_data)
 
     def current_state(self, chat_id):
         """Current state."""
-        states_data = self._read_data()
+        states_data = self.read_data()
         if chat_id in states_data: return states_data[chat_id]['state']
         else: return False
 
     def delete_state(self, chat_id):
         """Delete a state"""
-        states_data = self._read_data()
+        states_data = self.read_data()
         states_data.pop(chat_id)
-        self._save_data(states_data)
+        self.save_data(states_data)
 
-    def _read_data(self):
+    def read_data(self):
         """
         Read the data from file.
         """
@@ -247,7 +246,7 @@ class StateFile:
         file.close()
         return states_data
 
-    def _create_dir(self):
+    def create_dir(self):
         """
         Create directory .save-handlers.
         """
@@ -257,7 +256,7 @@ class StateFile:
             with open(self.file_path,'wb') as file:
                 pickle.dump({}, file)
         
-    def _save_data(self, new_data):
+    def save_data(self, new_data):
         """
         Save data after editing.
         :param new_data:
@@ -266,23 +265,21 @@ class StateFile:
             pickle.dump(new_data, state_file, protocol=pickle.HIGHEST_PROTOCOL)
         return True
 
-    def _get_data(self, chat_id):
-        return self._read_data()[chat_id]['data']
+    def get_data(self, chat_id):
+        return self.read_data()[chat_id]['data']
 
     def set(self, chat_id, new_state):
         """
         Set a new state for a user.
         :param chat_id:
         :param new_state: new_state of a user
-        
         """
         self.add_state(chat_id,new_state)
 
-    def _add_data(self, chat_id, key, value):
-        states_data = self._read_data()
+    def add_data(self, chat_id, key, value):
+        states_data = self.read_data()
         result = states_data[chat_id]['data'][key] = value
-        self._save_data(result)
-
+        self.save_data(result)
         return result
 
     def finish(self, chat_id):
@@ -313,7 +310,7 @@ class StateContext:
     def __init__(self , obj: StateMemory, chat_id) -> None:
         self.obj = obj
         self.chat_id = chat_id
-        self.data = obj._get_data(chat_id)
+        self.data = obj.get_data(chat_id)
 
     def __enter__(self):
         return self.data
@@ -321,6 +318,7 @@ class StateContext:
     def __exit__(self, exc_type, exc_val, exc_tb):
         return
 
+
 class StateFileContext:
     """
     Class for data.
@@ -328,15 +326,14 @@ class StateFileContext:
     def __init__(self , obj: StateFile, chat_id) -> None:
         self.obj = obj
         self.chat_id = chat_id
-        self.data = self.obj._get_data(self.chat_id)
+        self.data = self.obj.get_data(self.chat_id)
 
     def __enter__(self):
         return self.data
 
     def __exit__(self, exc_type, exc_val, exc_tb):
-        old_data = self.obj._read_data()
+        old_data = self.obj.read_data()
         for i in self.data:
             old_data[self.chat_id]['data'][i] = self.data.get(i)
-        self.obj._save_data(old_data)
-
+        self.obj.save_data(old_data)
         return
diff --git a/telebot/util.py b/telebot/util.py
index 1ab6201..8ec6be6 100644
--- a/telebot/util.py
+++ b/telebot/util.py
@@ -4,6 +4,7 @@ import re
 import string
 import threading
 import traceback
+import warnings
 from typing import Any, Callable, List, Dict, Optional, Union
 
 # noinspection PyPep8Naming
@@ -436,7 +437,7 @@ def generate_random_token():
     return ''.join(random.sample(string.ascii_letters, 16))
 
 
-def deprecated(warn: bool=False, alternative: Optional[Callable]=None):
+def deprecated(warn: bool=True, alternative: Optional[Callable]=None):
     """
     Use this decorator to mark functions as deprecated.
     When the function is used, an info (or warning if `warn` is True) is logged.
@@ -445,12 +446,11 @@ def deprecated(warn: bool=False, alternative: Optional[Callable]=None):
     """
     def decorator(function):
         def wrapper(*args, **kwargs):
+            info = f"`{function.__name__}` is deprecated." + (f" Use `{alternative.__name__}` instead" if alternative else "")
             if not warn:
-                logger.info(f"`{function.__name__}` is deprecated." 
-                    + (f" Use `{alternative.__name__}` instead" if alternative else ""))
+                logger.info(info)
             else:
-                logger.warn(f"`{function.__name__}` is deprecated." 
-                    + (f" Use `{alternative.__name__}` instead" if alternative else ""))
+                logger.warning(info)
             return function(*args, **kwargs)
         return wrapper
     return decorator
@@ -484,6 +484,7 @@ def antiflood(function, *args, **kwargs):
     """
     from telebot.apihelper import ApiTelegramException
     from time import sleep
+    msg = None
     try:
         msg = function(*args, **kwargs)
     except ApiTelegramException as ex:
@@ -491,4 +492,4 @@ def antiflood(function, *args, **kwargs):
             sleep(ex.result_json['parameters']['retry_after'])
             msg = function(*args, **kwargs)
     finally:
-        return msg
\ No newline at end of file
+        return msg
diff --git a/telebot/version.py b/telebot/version.py
index 42af8f6..531afbd 100644
--- a/telebot/version.py
+++ b/telebot/version.py
@@ -1,3 +1,3 @@
 # Versions should comply with PEP440.
 # This line is parsed in setup.py:
-__version__ = '4.3.0'
+__version__ = '4.3.1'
diff --git a/tests/test_telebot.py b/tests/test_telebot.py
index 2976a9a..54d3807 100644
--- a/tests/test_telebot.py
+++ b/tests/test_telebot.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import sys
+import warnings
 
 sys.path.append('../')
 
@@ -19,14 +20,19 @@ if not should_skip:
     CHAT_ID = os.environ['CHAT_ID']
     GROUP_ID = os.environ['GROUP_ID']
 
-def _new_test():
-    pass
 
-@util.deprecated(alternative=_new_test)
-def _test():
-    pass
-        
+def deprecated1_new_function():
+    print("deprecated1_new_function")
+def deprecated1_old_function():
+    print("deprecated1_old_function")
+    warnings.warn("The 'deprecated1_old_function' is deprecated. Use `deprecated1_new_function` instead", DeprecationWarning, 2)
+    deprecated1_new_function()
 
+def deprecated2_new_function():
+    print("deprecated2_new_function")
+@util.deprecated(alternative=deprecated2_new_function)
+def deprecated2_old_function():
+    print("deprecated2_old_function")
 
 @pytest.mark.skipif(should_skip, reason="No environment variables configured")
 class TestTeleBot:
@@ -216,7 +222,7 @@ class TestTeleBot:
     def test_send_audio(self):
         file_data = open('./test_data/record.mp3', 'rb')
         tb = telebot.TeleBot(TOKEN)
-        ret_msg = tb.send_audio(CHAT_ID, file_data, 1, performer='eternnoir', title='pyTelegram')
+        ret_msg = tb.send_audio(CHAT_ID, file_data, duration = 1, performer='eternnoir', title='pyTelegram')
         assert ret_msg.content_type == 'audio'
         assert ret_msg.audio.performer == 'eternnoir'
         assert ret_msg.audio.title == 'pyTelegram'
@@ -224,7 +230,7 @@ class TestTeleBot:
     def test_send_audio_dis_noti(self):
         file_data = open('./test_data/record.mp3', 'rb')
         tb = telebot.TeleBot(TOKEN)
-        ret_msg = tb.send_audio(CHAT_ID, file_data, 1, performer='eternnoir', title='pyTelegram',
+        ret_msg = tb.send_audio(CHAT_ID, file_data, duration = 1, performer='eternnoir', title='pyTelegram',
                                 disable_notification=True)
         assert ret_msg.content_type == 'audio'
         assert ret_msg.audio.performer == 'eternnoir'
@@ -433,8 +439,10 @@ class TestTeleBot:
 
     def test_create_revoke_detailed_chat_invite_link(self):
         tb = telebot.TeleBot(TOKEN)
-        cil = tb.create_chat_invite_link(GROUP_ID, 
-            (datetime.now() + timedelta(minutes=1)).timestamp(), member_limit=5)
+        cil = tb.create_chat_invite_link(
+            GROUP_ID,
+            expire_date = datetime.now() + timedelta(minutes=1),
+            member_limit=5)
         assert isinstance(cil.invite_link, str)
         assert cil.creator.id == tb.get_me().id
         assert isinstance(cil.expire_date, (float, int))
@@ -458,9 +466,10 @@ class TestTeleBot:
     def test_antiflood(self):
         text = "Flooding"
         tb = telebot.TeleBot(TOKEN)
-        for _ in range(0,100):
+        i = -1
+        for i in range(0,100):
             util.antiflood(tb.send_message, CHAT_ID, text)
-        assert _
+        assert i
 
     @staticmethod
     def create_text_message(text):
@@ -579,14 +588,14 @@ class TestTeleBot:
         ret_msg = tb.set_my_commands([telebot.types.BotCommand(command, description)], scope, lang)
         assert ret_msg is True
 
-        ret_msg = tb.get_my_commands(scope, lang)
+        ret_msg = tb.get_my_commands(scope = scope, language_code = lang)
         assert ret_msg[0].command == command
         assert ret_msg[0].description == description
 
-        ret_msg = tb.delete_my_commands(scope, lang)
+        ret_msg = tb.delete_my_commands(scope = scope, language_code = lang)
         assert ret_msg is True
 
-        ret_msg = tb.get_my_commands(scope, lang)
+        ret_msg = tb.get_my_commands(scope = scope, language_code = lang)
         assert ret_msg == []
 
 
@@ -633,7 +642,8 @@ class TestTeleBot:
         assert update.message.text == 'got' * 2
     
     def test_deprecated_dec(self):
-        _test()
+        deprecated1_old_function()
+        deprecated2_old_function()
 
     def test_chat_permissions(self):
         return # CHAT_ID is private chat, no permissions can be set