Identifier of the chat in which to count messages.
Filter for message content; searchMessagesFilterEmpty is unsupported in this function.
Optional
return_Pass true to get the number of messages without sending network requests, or -1 if the number of messages is unknown locally.
Pass topic identifier to get number of messages only in specific topic; pass null to get number of messages in all topics.
Returns approximate number of messages of the specified type in the chat or its topic. Request type for Tdjson#getChatMessageCount.