class_docstr: Helper for mocking subprocess calls
code: def which(self, name: str) -> tp.Optional[str]:
      return "here" if name in self.known_cmds else None
  
imports: import contextlib
  import pickle
  import subprocess
  import sys
  import time
  import typing
  from pathlib import Path
  from unittest.mock import patch
  import pytest
  from .None import core, submission, utils
label_desc: Use image node_id 8 for calling the MockedSubprocess obj's underlying member method code with example usage: obj.which(name) and returns: unknown