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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 pick(self, acr=None):
 """ Given the authentication context find zero or more authn methods that could be used. :param acr: The authentication class reference requested :return: An URL """


        if acr is None:
            # Anything else doesn't make sense
            return self.db.values()
        else:
            return self._pick_by_class_ref(acr)