code: def get_shell(pid=None, max_depth=6):
      
      pid = str(pid or os.getpid())
      mapping = _get_process_mapping()
      for proc_cmd in _iter_process_command(mapping, pid, max_depth):
          if proc_cmd.startswith('-'):    # Login shell! Let's use this.
              return _get_login_shell(proc_cmd)
          name = os.path.basename(proc_cmd).lower()
          if name in SHELL_NAMES:     # The inner-most (non-login) shell.
              return (name, proc_cmd)
      return None
docs: Get the shell that the supplied pid or os.getpid() is running in.