code: def concat_callback(
      app, flavor, outputs, inputs, prevent_initial_call=False
  ):
      kwargs = {}
      if prevent_initial_call != flavor["global"]:
          kwargs["prevent_initial_call"] = prevent_initial_call
  
      multi_out = isinstance(outputs, (list, tuple))
  
      if flavor["clientside"]:
          app.clientside_callback(
              """
              function() {
                  var out = '';
                  for(var i = 0; i < arguments.length; i++) {
                      out += String(arguments[i]);
                  }
                  return X;
              }
              """.replace(
                  "X",
                  ("[" + ",".join(["out"] * len(outputs)) + "]")
                  if multi_out
                  else "out",
              ),
              outputs,
              inputs,
              **kwargs,
          )
      else:
  
          @app.callback(outputs, inputs, **kwargs)
          def f(*args):
              out = "".join(str(arg) for arg in args)
              return [out] * len(outputs) if multi_out else out
  
file_path: dash/tests/integration/callbacks/test_prevent_initial.py
imports: import json
  import pytest
  from flaky import flaky
  from dash import Dash, Input, Output, MATCH, html
  from dash.exceptions import PreventUpdate
label_desc: Use image node_id 4 for calling a global function with example usage: concat_callback(app, flavor, outputs, inputs, prevent_initial_call) and returns: unknown