docs: public DoubleProperty lengthProperty() {
  		if (this.length == null) {
  			this.length = new ReadOnlyDoubleWrapper();
  			this.length.bind(Bindings.createDoubleBinding(() -> Path2afp.calculatesPathLength(getPathIterator()),
  					innerTypesProperty(), innerCoordinatesProperty()));
  		}
  		return this.length;
  	}