Как метод handle_delivery реализован в pika Python?

Question

Я пытаюсь понять этот пример кода из введения в pika ( http://pika.readthedocs.io/en/0.10.0/intro.html):

import pika

# Create a global channel variable to hold our channel object in
channel = None

# Step #2
def on_connected(connection):
    """Called when we are fully connected to RabbitMQ"""
    # Open a channel
    connection.channel(on_channel_open)

# Step #3
def on_channel_open(new_channel):
    """Called when our channel has opened"""
    global channel
    channel = new_channel
    channel.queue_declare(queue="test", durable=True, exclusive=False, auto_delete=False, callback=on_queue_declared)

# Step #4
def on_queue_declared(frame):
    """Called when RabbitMQ has told us our Queue has been declared, frame is the response from RabbitMQ"""
    channel.basic_consume(handle_delivery, queue='test')

# Step #5
def handle_delivery(channel, method, header, body):
    """Called when we receive a message from RabbitMQ"""
    print body

# Step #1: Connect to RabbitMQ using the default parameters
parameters = pika.ConnectionParameters()
connection = pika.SelectConnection(parameters, on_connected)

try:
    # Loop so we can communicate with RabbitMQ
    connection.ioloop.start()
except KeyboardInterrupt:
    # Gracefully close the connection
    connection.close()
    # Loop until we're fully closed, will stop on its own
    connection.ioloop.start()

Согласно документации строки для handle_delivery, он должен быть вызван, когда мы получим сообщение от RabbitMQ. Тем не менее, я не вижу этого handle_delivery далее упоминается в коде, и я не нахожу его в исходном коде pika 0.10.0:

kurt@kurt-ThinkPad:~/dev/scratch/pika-0.10.0$ grep -r "handle_delivery"
kurt@kurt-ThinkPad:~/dev/scratch/pika-0.10.0$ 

Так как же handle_delivery быть "поднятым" connection?

Answer 1

step4 связывает канал с функцией handle_deivery.

# Step #4
def on_queue_declared(frame):
    """Called when RabbitMQ has told us our Queue has been declared, frame is the response from RabbitMQ"""
    channel.basic_consume(handle_delivery, queue='test')

Канал связан с соединением на шаге № 2

# Step #2
def on_connected(connection):
    """Called when we are fully connected to RabbitMQ"""
    # Open a channel
    connection.channel(on_channel_open)