private static function loadItems($property_id)
	{
		self::$_items[$property_id] = [];
		$models = static::find()
			->where('property_id=:property_id', [':property_id' => $property_id])
			->orderBy('position')
			->all();
		foreach($models as $model)
			self::$_items[$property_id][$model->code] = $model->name;
	}