protected function map_filter( $id, $method, $arg_count ) {
		if ( empty( $this->filter_map[ $id ] ) ) {
			$this->filter_map[ $id ] = function () use ( $method, $arg_count ) {
				return call_user_func_array( [ $this, $method ], array_slice( func_get_args(), 0, $arg_count ) );
			};
		}

		return $this->filter_map[ $id ];
	}