docs: def _fill_out_err(result, testcase):
          """Adds stdout and stderr if present."""
          if result.get("stdout"):
              system_out = etree.SubElement(testcase, "system-out")
              system_out.text = utils.get_unicode_str(result["stdout"])
  
          if result.get("stderr"):
              system_err = etree.SubElement(testcase, "system-err")
              system_err.text = utils.get_unicode_str(result["stderr"])