protected function get_compute_methods() {
		$methods = get_class_methods( get_called_class() );
		$methods = array_filter( $methods, function ( $method ) {
			return strrpos( $method, 'compute_', - strlen( $method ) ) !== false;
		} );
		$methods = array_map( function ( $method ) {
			return substr( $method, strlen( 'compute_' ) );
		}, $methods );

		return $methods;
	}