code: def test_on():
      with pytest.raises(TypeError):
  
          @Trainer.on(Event.on_before_backward())
          def before_backend():
              pass
  
      @Trainer.on(Event.on_before_backward())
      def before_backend(*args):
          pass
  
      with pytest.raises(TypeError):
  
          @Trainer.on(Event.on_before_backward())
          def before_backend(*args, s):
              pass
  
      @Trainer.on(Event.on_before_backward())
      def before_backend(*args, s=2):
          pass
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_on() without return types