public static function get_instance( $id = 'global', $args = [] ) {
		if ( empty( $id ) ) {
			$id = 'global';
		}
		$id_md5 = md5( $id );
		if ( ! isset( self::$instances[ $id_md5 ] ) ) {
			self::$instances[ $id_md5 ] = new self( $id, $args );
		}
		return self::$instances[ $id_md5 ];
	}