def on_connection_open(self, _):
logger.debug('<STR_LIT>')<EOL>self.add_on_connection_close_callback()<EOL>self.open_channel()<EOL>
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 _: pika.SelectConnection