code: def test_import_vispy_app2():
      """Importing vispy.app should not pull in any backend toolkit."""
      allmodnames = loaded_vispy_modules("vispy.app", 2, True)
      assert_not_in("PySide", allmodnames)
      assert_not_in("PySide2", allmodnames)
      assert_not_in("PySide6", allmodnames)
      assert_not_in("PyQt4", allmodnames)
      assert_not_in("PyQt5", allmodnames)
      assert_not_in("PyQt6", allmodnames)
      assert_not_in("pyglet", allmodnames)
  
file_path: vispy/vispy/util/tests/test_import.py
imports: import sys
  import os
  from vispy.testing import assert_in, assert_not_in, requires_pyopengl, run_tests_if_main, assert_equal
  from vispy.util import run_subprocess
  import vispy
label_desc: Use image node_id 6 for calling a global function with example usage: test_import_vispy_app2() without return types