code: def basic_ack(self, delivery_tag, multiple=False):
          
          args = AMQPWriter()
          args.write_longlong(delivery_tag)
          args.write_bit(multiple)
          self._send_method((60, 80), args)
docs: Acknowledge one or more messages
  
          This method acknowledges one or more messages delivered via
          the Deliver or Get-Ok methods.  The client can ask to confirm
          a single message or a set of messages up to and including a
          specific message.
  
          PARAMETERS:
              delivery_tag: longlong
  
                  server-assigned delivery tag
  
                  The server-assigned and channel-specific delivery tag
  
                  RULE:
  
                      The delivery tag is valid only within the channel
                      from which the message was received.  I.e. a client
                      MUST NOT receive a message on one channel and then
                      acknowledge it on another.
  
                  RULE:
  
                      The server MUST NOT use a zero value for delivery
                      tags.  Zero is reserved for client use, meaning "all
                      messages so far received".
  
              multiple: boolean
  
                  acknowledge multiple messages
  
                  If set to True, the delivery tag is treated as "up to
                  and including", so that the client can acknowledge
                  multiple messages with a single method.  If set to
                  False, the delivery tag refers to a single message.
                  If the multiple field is True, and the delivery tag
                  is zero, tells the server to acknowledge all
                  outstanding mesages.
  
                  RULE:
  
                      The server MUST validate that a non-zero delivery-
                      tag refers to an delivered message, and raise a
                      channel exception if this is not the case.