code: def render_fn_no_args():
      """Test function with no arguments."""
      return "no_args"
  
file_path: pytorch-lightning/tests/tests_app/frontend/panel/test_panel_serve_render_fn.py
imports: import inspect
  import os
  from unittest import mock
  import pytest
  from lightning.app.frontend.panel.app_state_watcher import AppStateWatcher
  from lightning.app.frontend.panel.panel_serve_render_fn import _get_render_fn, _get_render_fn_from_environment
  from lightning_utilities.core.imports import RequirementCache
label_desc: Use image node_id 4 for calling a global function with example usage: render_fn_no_args() and returns: str