code: def save_file(self, filename, target_name=None):
      target_name = target_name or os.path.basename(filename)
      blacklist = [
          "run.json",
          "config.json",
          "cout.txt",
          "metrics.json",
      ]
      blacklist = [os.path.join(self.dir, x) for x in blacklist]
      dest_file = os.path.join(self.dir, target_name)
      if dest_file in blacklist:
          raise FileExistsError(
              "You are trying to overwrite a file necessary for the "
              "FileStorageObserver. "
              "The list of blacklisted files is: {}".format(blacklist)
          )
      try:
          copyfile(filename, dest_file)
      except SameFileError:
          pass
  
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 13 for calling the FileStorageObserver obj's underlying member method code with example usage: obj.save_file(filename, target_name) without return types