@abc.abstractmethod<EOL><INDENT>def add_composition_child(self, composition_id, child_composition_id):<DEDENT>
pass<EOL>
Adds a composition to a parent composition.

        :param composition_id: the ``Id`` of a parent ``Composition``
        :type composition_id: ``osid.id.Id``
        :param child_composition_id: the ``Id`` of a child ``Composition``
        :type child_composition_id: ``osid.id.Id``
        :raise: ``AlreadyExists`` -- ``child_composition_id`` is already a child of ``composition_id``
        :raise: ``NotFound`` -- ``composition_id`` or ``child_composition_id`` is not found
        :raise: ``NullArgument`` -- ``composition_id`` or ``child_composition_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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