def get_authority(self):
return self._authority<EOL>
Gets the authority of this ``Id``.

        The authority is a string used to ensure the uniqueness of this
        ``Id`` when using a non- federated identifier space. Generally,
        it is a service name identifying the provider of this ``Id``.
        This method is used to compare one ``Id`` to another.

        return: (string) - the authority of this ``Id``
        *compliance: mandatory -- This method must be implemented.*