code: def _check_generated_stderr(self, stderr, n):
      expected = [
          r"\[stderr:\d+\]",
          "^stderr$",
          "^stderr2$",
      ] * n
  
      assert "\n\n" not in stderr
      lines = stderr.splitlines()
      assert len(lines), len(expected) == stderr
      for line, expect in zip(lines, expected):
          if isinstance(expect, str):
              expect = [expect]
          for ex in expect:
              assert (
                  re.search(ex, line) is not None
              ), f"Expected {ex!r} in {line!r}"
  
imports: import re
  import signal
  import sys
  import time
  import pytest
  from IPython import get_ipython
  from IPython.utils.io import capture_output
  import ipyparallel
  from ipyparallel import AsyncResult
  from .clienttest import ClusterTestCase, generate_output, raises_remote
label_desc: Use image node_id 4 for calling the TestParallelMagics obj's underlying member method code with example usage: obj._check_generated_stderr(stderr, n) without return types