code: def _calculate_namespace(
      self, logdir: str, rootdir: str
  ) -> Optional[str]:
      namespace: Optional[str]
      dirs = list(self._logdirs) + [logdir]
  
      if os.path.isfile(logdir):
          filename = os.path.basename(logdir)
      else:
          filename = ""
  
      if rootdir == "":
          rootdir = util.to_forward_slash_path(
              os.path.dirname(os.path.commonprefix(dirs))
          )
          # Tensorboard loads all tfevents files in a directory and prepends
          # their values with the path. Passing namespace to log allows us
          # to nest the values in wandb
          # Note that we strip '/' instead of os.sep, because elsewhere we've
          # converted paths to forward slash.
          namespace = (
              logdir.replace(filename, "")
              .replace(rootdir, "")
              .strip("/")
          )
  
          # TODO: revisit this heuristic, it exists because we don't know the
          # root log directory until more than one tfevents file is written to
          if len(dirs) == 1 and namespace not in [
              "train",
              "validation",
          ]:
              namespace = None
      else:
          namespace = (
              logdir.replace(filename, "")
              .replace(rootdir, "")
              .strip("/")
          )
  
      return namespace
  
imports: import glob
  import logging
  import os
  import queue
  import socket
  import sys
  import threading
  import time
  from typing import TYPE_CHECKING, Any, Dict, List, Optional
  import wandb
  from wandb import util
  from wandb.sdk.interface.interface import GlobStr
  from wandb.sdk.lib import filesystem
  from wandb.viz import CustomChart
  from .None import run
label_desc: Use image node_id 2 for calling the TBWatcher obj's underlying member method code with example usage: obj._calculate_namespace(logdir, rootdir) and returns: namespace