def get_copyright(self):
return self._payload.get_copyright()<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        original copyright statement although it may be no longer valid.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: (osid.locale.DisplayText) - the copyright statement or
                an empty string if none available. An empty string does
                not imply the asset is not protected by copyright.
        raise:  IllegalState - ``is_copyright_status_known()`` is
                ``false``
        *compliance: mandatory -- This method must be implemented.*