@abc.abstractmethod<EOL><INDENT>def get_composition_id(self):<DEDENT>
return<EOL>
Gets the ``Composition``  ``Id`` corresponding to this asset.

        :return: the composiiton ``Id``
        :rtype: ``osid.id.Id``
        :raise: ``IllegalState`` -- ``is_composition()`` is ``false``

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