code: def test_xml_filters_round_trip():
      """Ensure doing nothing does nothing"""
      plot = Bar()
      plot.add("A", [60, 75, 80, 78, 83, 90])
      plot.add("B", [92, 87, 81, 73, 68, 55])
      before = plot.render()
      plot.add_xml_filter(lambda T: T)
      after = plot.render()
      assert before == after
  
imports: from pygal import Bar
label_desc: Use image node_id 1 for calling a global function with example usage: test_xml_filters_round_trip() without return types