code: def test_dync002_dynamic_callback_without_element(dash_duo):
      app = Dash()
  
      app.layout = html.Div(
          [
              html.Button("Add callbacks", id="add-callbacks"),
              html.Div(id="output"),
          ]
      )
  
      @app.callback(
          Output("output", "children"),
          Input("add-callbacks", "n_clicks"),
          _allow_dynamic_callbacks=True,
          prevent_initial_call=True,
      )
      def on_add_callback(_):
          @app.callback(
              Output("no-exist", "children"),
              Input("invalid", "n_clicks"),
          )
          def addition(_):
              return "additional"
  
          return html.Div("add callbacks")
  
      dash_duo.start_server(app)
  
      dash_duo.wait_for_element("#add-callbacks").click()
      dash_duo.wait_for_text_to_equal("#output", "add callbacks")
  
      assert dash_duo.get_logs() == []
  
label_desc: Use image node_id 2 for calling a global function with example usage: test_dync002_dynamic_callback_without_element(dash_duo) and returns: html, str