@abc.abstractmethod<EOL><INDENT>def add_asset_spatial_coverage(self, asset_id, spatial_unit):<DEDENT>
pass<EOL>
Adds a spatial coverage to an asset.

        :param asset_id: ``Id`` of the ``Asset``
        :type asset_id: ``osid.id.Id``
        :param spatial_unit: spatial coverage
        :type spatial_unit: ``osid.mapping.SpatialUnit``
        :raise: ``AlreadyExists`` -- asset already contains this spatial coverage
        :raise: ``NotFound`` -- ``asset_id`` not ``found``
        :raise: ``NullArgument`` -- ``asset_id`` or ``spatial_unit`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization fauilure
        :raise: ``Unsupported`` -- ``spatial_unit`` not supported

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