1. DomName('SVGNumberList.insertItemBefore')
  2. DocsEditable()
Number insertItemBefore(Number newItem, int index)

Source 

@DomName('SVGNumberList.insertItemBefore')
@DocsEditable()
Number insertItemBefore(Number newItem, int index) => _blink.BlinkSVGNumberList.instance.insertItemBefore_Callback_2_(this, newItem, index);