'Turn Channel flow control off and on. Pass a callback to be notified
of the response from the server. active is a bool. Callback should
expect a bool in response indicating channel flow state. For more
information, please reference:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#channel.flow
:param callable callback: The callback to call upon completion
:param bool active: Turn flow on or off'

def flow(self, callback, active):

    self._validate_channel_and_callback(callback)
    self._on_flowok_callback = callback
    self._rpc(spec.Channel.Flow(active), self._on_flowok, [spec.Channel.FlowOk])
