code: protected void registerListAttributes() {
          addAttributeProcessor(new MultipleLmlAttribute(), "multiple");
          addAttributeProcessor(new RangeSelectLmlAttribute(), "rangeSelect");
          addAttributeProcessor(new RequiredLmlAttribute(), "required");
          addAttributeProcessor(new SelectedLmlAttribute(), "selected", "select", "value");
          addAttributeProcessor(new SelectionDisabledLmlAttribute(), "disabled", "disable");
          addAttributeProcessor(new ToggleLmlAttribute(), "toggle");
      }
docs: List widget attributes.