code: def test_identifier():
      assert (
          re.match("(" + re_identifier + ")", "Ax2_d3__7").groups()[0]
          == "Ax2_d3__7"
      )
      assert (
          re.match("(" + re_identifier + ")", "_Ax2_d3__7").groups()[0]
          == "_Ax2_d3__7"
      )
      assert re.match(re_identifier, "7Ax2_d3__7") is None
      assert (
          re.match("(" + re_identifier + ")", "x,y").groups()[0] == "x"
      )
      assert (
          re.match("(" + re_identifier + ")", "x y").groups()[0] == "x"
      )
  
imports: import re
  from vispy.visuals.shaders.parsing import re_identifier, find_program_variables
  from vispy.testing import run_tests_if_main
label_desc: Use image node_id 1 for calling a global function with example usage: test_identifier() without return types