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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 authenticate(self, auth_token, auth_info, service_name):
 """Authenticates the current auth token. Args: auth_token: the auth token. auth_info: the auth configurations of the API method being called. service_name: the name of this service. Returns: A constructed UserInfo object representing the identity of the caller. Raises: UnauthenticatedException: When * the issuer is not allowed; * the audiences are not allowed; * the auth token has already expired. """

        try:
            jwt_claims = self.get_jwt_claims(auth_token)
        except Exception as error:
            raise suppliers.UnauthenticatedException(u"Cannot decode the auth token",
                                                     error)
        _check_jwt_claims(jwt_claims)

        user_info = UserInfo(jwt_claims)

        issuer = user_info.issuer
        if issuer not in self._issuers_to_provider_ids:
            raise suppliers.UnauthenticatedException(u"Unknown issuer: " + issuer)
        provider_id = self._issuers_to_provider_ids[issuer]

        if not auth_info.is_provider_allowed(provider_id):
            raise suppliers.UnauthenticatedException(u"The requested method does not "
                                                     u"allow provider id: " + provider_id)

        # Check the audiences decoded from the auth token. The auth token is
        # allowed when 1) an audience is equal to the service name, or 2) at least
        # one audience is allowed in the method configuration.
        audiences = user_info.audiences
        has_service_name = service_name in audiences

        allowed_audiences = auth_info.get_allowed_audiences(provider_id)
        intersected_audiences = set(allowed_audiences).intersection(audiences)
        if not has_service_name and not intersected_audiences:
            raise suppliers.UnauthenticatedException(u"Audiences not allowed")

        return user_info