@abc.abstractmethod<EOL><INDENT>def get_copyright_registration(self):<DEDENT>
return<EOL>
Gets the copyright registration information for this asset.

        :return: the copyright registration. An empty string means the registration status isn't known.
        :rtype: ``string``
        :raise: ``IllegalState`` -- ``is_copyright_status_known()`` is ``false``

        *compliance: mandatory -- This method must be implemented.*