'Set the message class that should be used when instantiating
messages read from the queue.  By default, the class
:class:`boto.sqs.message.Message` is used but this can be overriden
with any class that behaves like a message.
:type message_class: Message-like class
:param message_class:  The new Message class'

def set_message_class(self, message_class):

    self.message_class = message_class
