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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 expose(policy):
 """ Annotate a method to permit access to contexts matching an authorization policy. The annotation may be specified multiple times. Methods lacking any authorization policy are not accessible. :: @mitogen.service.expose(policy=mitogen.service.AllowParents()) def unsafe_operation(self):
 :param mitogen.service.Policy policy: The policy to require. """

    def wrapper(func):
        func.mitogen_service__policies = (
            [policy] +
            getattr(func, 'mitogen_service__policies', [])
        )
        return func
    return wrapper