docs: def _on_message(channel, method, header, body):
      """
      Invoked by pika when a message is delivered from RabbitMQ. The
      channel is passed for your convenience. The basic_deliver object that
      is passed in carries the exchange, routing key, delivery tag and
      a redelivered flag for the message. The properties passed in is an
      instance of BasicProperties with the message properties and the body
      is the message that was sent.
  
      :param pika.channel.Channel channel: The channel object
      :param pika.Spec.Basic.Deliver method: The Deliver method
      :param pika.Spec.BasicProperties properties: The client properties
      :param str|unicode body: The message body
      """
      print "Message:"
      print "\t%r" % method
      print "\t%r" % header
      print "\t%r" % body
  
      # Acknowledge message receipt
      channel.basic_ack(method.delivery_tag)
  
      # when ready, stop consuming
      channel.stop_consuming()