code: def test_dvcv001_blank(dash_duo):
      app = Dash(__name__)
      app.layout = html.Div()
  
      @app.callback([], [])
      def x():
          return 42
  
      dash_duo.start_server(app, **debugging)
      check_errors(
          dash_duo,
          [
              [
                  "A callback is missing Inputs",
                  ["there are no `Input` elements."],
              ],
              [
                  "A callback is missing Outputs",
                  ["Please provide an output for this callback:"],
              ],
          ],
      )
  
imports: import flask
  import pytest
  from dash import Dash, Input, Output, State, MATCH, ALL, ALLSMALLER, html, dcc
  from dash.testing import wait
label_desc: Use image node_id 2 for calling a global function with example usage: test_dvcv001_blank(dash_duo) and returns: int