Fix 3.8 syntax warning and erroneous documentation

Closes #1340 (syntax warning)
Closes #1341 (outdated docs)

telethon/client/auth.py

@@ -464,11 +464,6 @@ class AuthMethods:
                 phone = '+34 123 123 123'
                 sent = await client.send_code_request(phone)
                 print(sent)
-
-                if sent.phone_registered:
-                    print('This phone has an existing account registered')
-                else:
-                    print('This phone does not have an account registered')
         """
         result = None
         phone = utils.parse_phone(phone) or self._phone

telethon/client/messageparse.py

@@ -75,7 +75,7 @@ class MessageParseMethods:
         """
         Returns a (parsed message, entities) tuple depending on ``parse_mode``.
         """
-        if parse_mode is ():
+        if parse_mode == ():
             parse_mode = self._parse_mode
         else:
             parse_mode = utils.sanitize_parse_mode(parse_mode)

telethon/client/messages.py

@@ -501,7 +501,7 @@ class MessageMethods:
                 photos = await client.get_messages(chat, None, filter=InputMessagesFilterPhotos)
 
                 # Get messages by ID:
-                message_1337 = await client.get_messages(chats, ids=1337)
+                message_1337 = await client.get_messages(chat, ids=1337)
         """
         if len(args) == 1 and 'limit' not in kwargs:
             if 'min_id' in kwargs and 'max_id' in kwargs: