@abc.abstractmethod<EOL><INDENT>def add_asset(self, asset_id, composition_id):<DEDENT>
pass<EOL>
Appends an asset to a composition.

        :param asset_id: ``Id`` of the ``Asset``
        :type asset_id: ``osid.id.Id``
        :param composition_id: ``Id`` of the ``Composition``
        :type composition_id: ``osid.id.Id``
        :raise: ``AlreadyExists`` -- ``asset_id`` already part ``composition_id``
        :raise: ``NotFound`` -- ``asset_id`` or ``composition_id`` not found
        :raise: ``NullArgument`` -- ``asset_id`` or ``composition_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization fauilure

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