def ack(messageid, transactionid=None):
header = '<STR_LIT>' % messageid<EOL>if transactionid:<EOL><INDENT>header = '<STR_LIT>' % (messageid, transactionid)<EOL><DEDENT>return "<STR_LIT>" % header<EOL>
STOMP acknowledge command.

    Acknowledge receipt of a specific message from the server.

    messageid:
        This is the id of the message we are acknowledging,
        what else could it be? ;)

    transactionid:
        This is the id that all actions in this transaction
        will have. If this is not given then a random UUID
        will be generated for this.