docs: def addClef(self, item, voice=1):
          '''
          method to use when adding a clef. will either add it to the node itself or add it onto the first voice's children
          list
          :param item:
          :param voice:
          :return:
          '''
          if not hasattr(self, "clef"):
              self.clef = item
          else:
              voice_obj = self.GetChild(voice)
              node = ClefNode()
              node.SetItem(item)
              if voice_obj is not None:
                  voice_obj.AddChild(node)
                  self.index += 1