code: def on_connection_open(self, unused_connection):
          
          self._logger.info('Connection opened')
          self.add_on_connection_close_callback()
          self.open_channel()
docs: Called by pika once the connection to RabbitMQ has
          been established. It passes the handle to the connection object in
          case we need it, but in this case, we'll just mark it unused.
  
          :type unused_connection: pika.SelectConnection