def get_authentication(self):
if self.has_authentication():<EOL><INDENT>return self._authentication<EOL><DEDENT>else:<EOL><INDENT>raise errors.IllegalState()<EOL><DEDENT>
Gets the ``Authentication`` for this proxy.

        return: (osid.authentication.process.Authentication) - the
                authentication
        raise:  IllegalState - ``has_authentication()`` is ``false``
        *compliance: mandatory -- This method must be implemented.*