code: def add_asset(self, asset_id, composition_id):
          
          self._provider_session.add_asset(self, asset_id, composition_id)
docs: Appends an asset to a composition.
  
          arg:    asset_id (osid.id.Id): ``Id`` of the ``Asset``
          arg:    composition_id (osid.id.Id): ``Id`` of the
                  ``Composition``
          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.*