code: def test_check_identifier():
      # Tests check_identifier()
      assert util.check_identifier("foo") is None
      assert util.check_identifier("_fooBarBla") is None
      assert util.check_identifier("_glPosition") is None
  
      # Wrong identifier
      assert util.check_identifier("__").startswith("Identifier")
      assert util.check_identifier("gl_").startswith("Identifier")
      assert util.check_identifier("GL_").startswith("Identifier")
      assert util.check_identifier("double").startswith("Identifier")
  
      # Test check_variable()
      assert util.check_variable("foo") is None
      assert util.check_variable("a" * 30) is None
      assert util.check_variable("a" * 32)
  
imports: from vispy.gloo import util
  from vispy.testing import run_tests_if_main, assert_raises
label_desc: Use image node_id 2 for calling a global function with example usage: test_check_identifier() without return types