code: def test_dual(capsys):
      m.captured_dual("a", "b")
      stdout, stderr = capsys.readouterr()
      assert stdout == "a"
      assert stderr == "b"
  
imports: from contextlib import redirect_stderr, redirect_stdout
  from io import StringIO
  from pybind11_tests import iostream
label_desc: Use image node_id 18 for calling a global function with example usage: test_dual(capsys) without return types