<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_server_unread_messages_count(self, server_name=None):
 """Gets count of unread messages from server """

        server = self._servers.get(server_name)
        return server.get_messages_count_in_buffer()