code: def test_cbpu001_aborted_callback(dash_duo):
      """Raising PreventUpdate OR returning no_update prevents update and
      triggering dependencies."""
  
      initial_input = "initial input"
      initial_output = "initial output"
  
      app = Dash(__name__)
      app.layout = html.Div(
          [
              dcc.Input(id="input", value=initial_input),
              html.Div(initial_output, id="output1"),
              html.Div(initial_output, id="output2"),
          ]
      )
  
      callback1_count = Value("i", 0)
      callback2_count = Value("i", 0)
  
      @app.callback(
          Output("output1", "children"), [Input("input", "value")]
      )
      def callback1(value):
          callback1_count.value += 1
          if callback1_count.value > 2:
              return no_update
          raise PreventUpdate("testing callback does not update")
          return value
  
      @app.callback(
          Output("output2", "children"), [Input("output1", "children")]
      )
      def callback2(value):
          callback2_count.value += 1
          return value
  
      dash_duo.start_server(app)
  
      input_ = dash_duo.find_element("#input")
      for i, key in enumerate("xyz"):
          input_.send_keys(key)
          until(
              lambda: callback1_count.value == i + 2,
              timeout=3,
              msg="callback1 runs 4x (initial page load and 3x through send_keys)",
          )
  
      dash_duo.wait_for_text_to_equal("#input", "initial inputxyz")
  
      assert (
          callback2_count.value == 0
      ), "callback2 is never triggered, even on initial load"
  
      # double check that output1 and output2 children were not updated
      assert dash_duo.find_element("#output1").text == initial_output
      assert dash_duo.find_element("#output2").text == initial_output
  
      assert not dash_duo.get_logs()
  
      dash_duo.percy_snapshot(name="aborted")
  
file_path: dash/tests/integration/callbacks/test_prevent_update.py
imports: from multiprocessing import Value
  from copy import copy
  from selenium.webdriver.common.keys import Keys
  from dash import Dash, no_update, Input, Output, State, html, dcc
  from dash.exceptions import PreventUpdate
  from dash.testing.wait import until
label_desc: Use image node_id 1 for calling a global function with example usage: test_cbpu001_aborted_callback(dash_duo) and returns: value, value, no_update