docs: def Forward(self, duration=0):
          '''
          method to use when forward tag is encountered in musicXML. jumps forward in the bar by <duration>
          :param duration: number of beats to move forward
          :return:
          '''
          for voice in self.GetChildrenIndexes():
              voice_obj = self.getVoice(voice)
              if voice_obj.GetChild(self.index) is None:
                  voice_obj.AddChild(NoteNode.NoteNode(duration=duration))
          self.index += 1