@abc.abstractmethod<EOL><INDENT>def get_copyright(self):<DEDENT>
return<EOL>
Gets the copyright statement and of this asset which identifies the current copyright holder.

        For an asset in the public domain, this method may return the
        original copyright statement although it may be no longer valid.

        :return: the copyright statement or an empty string if none available. An empty string does not imply the asset is not protected by copyright.
        :rtype: ``osid.locale.DisplayText``
        :raise: ``IllegalState`` -- ``is_copyright_status_known()`` is ``false``

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