public function blameable($fields = array('created', 'updated', 'deleted'), $nullable = false)
    {
        if (in_array('created', $fields)) {
            $this->createdBy($nullable);
        }

        if (in_array('updated', $fields)) {
            $this->updatedBy($nullable);
        }

        if (in_array('deleted', $fields)) {
            $this->deletedBy($nullable);
        }
    }