public function is_overridable_item() {
        if ($this->is_course_item() or $this->is_category_item()) {
            $overridable = (bool) get_config('moodle', 'grade_overridecat');
        } else {
            $overridable = false;
        }

        return !$this->is_outcome_item() and ($this->is_external_item() or $this->is_calculated() or $overridable);
    }