/**
* Returns a new model that is the subtraction of another model from this model.
*
* @param object Model $model
* @return object MemModel
* @access public
* @throws phpErrpr
*/
function subtract($model)
{
if (is_a($model, 'ResModel')) {
return $this->model->subtract($model->getModel());
}
return $this->model->subtract($model);
}
