code: def _maximum_existing_run_id(self):
      dir_nrs = [
          int(d)
          for d in os.listdir(self.basedir)
          if os.path.isdir(os.path.join(self.basedir, d))
          and d.isdigit()
      ]
      if dir_nrs:
          return max(dir_nrs)
      else:
          return 0
  
imports: import json
  import os
  import os.path
  from pathlib import Path
  from typing import Optional
  import warnings
  from shutil import copyfile, SameFileError
  from sacred.commandline_options import cli_option
  from sacred.dependencies import get_digest
  from sacred.observers.base import RunObserver
  from sacred import optional
  from sacred.serializer import flatten
  from sacred.utils import PathType
label_desc: Use image node_id 5 for calling the FileStorageObserver obj's underlying member method code with example usage: obj._maximum_existing_run_id() and returns: max, int