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
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: