Some small changes

* Fixed type warnings in some editors by changing `var: Type = None` to `var: Union[Type, None] = None`
* changed some args from `obj['arg']` to `obj.get('arg')` if arg is optional
* better PEP-8 compliance for less weak warnings
* added tests for the new type `ChatInviteLink`

tests/test_telebot.py

@@ -6,6 +6,7 @@ sys.path.append('../')
 import time
 import pytest
 import os
+from datetime import datetime, timedelta
 
 import telebot
 from telebot import types
@@ -407,6 +408,23 @@ class TestTeleBot:
         cn = tb.get_chat_members_count(GROUP_ID)
         assert cn > 1
 
+    def test_export_chat_invite_link(self):
+        tb = telebot.TeleBot(TOKEN)
+        il = tb.export_chat_invite_link(GROUP_ID)
+        assert isinstance(il, str)
+
+    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)
+        assert isinstance(cil.invite_link, str)
+        assert cil.creator.id == tb.get_me().id
+        assert isinstance(cil.expire_date, (float, int))
+        assert cil.member_limit == 5
+        assert not cil.is_revoked
+        rcil = tb.revoke_chat_invite_link(GROUP_ID, cil.invite_link)
+        assert rcil.is_revoked
+
     def test_edit_markup(self):
         text = 'CI Test Message'
         tb = telebot.TeleBot(TOKEN)

tests/test_types.py

@@ -219,3 +219,14 @@ def test_KeyboardButtonPollType():
     json_str = markup.to_json()
     assert 'request_poll' in json_str
     assert 'quiz' in json_str
+
+
+def test_json_chat_invite_link():
+    json_string = r'{"invite_link": "https://t.me/joinchat/z-abCdEFghijKlMn", "creator": {"id": 329343347, "is_bot": false, "first_name": "Test", "username": "test_user", "last_name": "User", "language_code": "en"}, "is_primary": false, "is_revoked": false, "expire_date": 1624119999, "member_limit": 10}'
+    invite_link = types.ChatInviteLink.de_json(json_string)
+    assert invite_link.invite_link == 'https://t.me/joinchat/z-abCdEFghijKlMn'
+    assert isinstance(invite_link.creator, types.User)
+    assert not invite_link.is_primary
+    assert not invite_link.is_revoked
+    assert invite_link.expire_date == 1624119999
+    assert invite_link.member_limit == 10