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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def message_to_event(zclient, msg):
 """ Converts Zebra protocol message instance to Zebra protocol service event instance. If corresponding event class is not defined, returns None. :param zclient: Zebra client instance. :param msg: Zebra protocol message. :return: Zebra protocol service event. """

    if not isinstance(msg, zebra.ZebraMessage):
        return None

    body_cls = msg.get_body_class(msg.version, msg.command)
    ev_cls = getattr(MOD, _event_name(body_cls), None)
    if ev_cls is None:
        return None

    return ev_cls(zclient, msg)