code: def set_fallback(self, fallback_filename):
      self.tpe = ThreadPoolExecutor()
      if not os.path.exists(fallback_filename):
          raise FileNotFoundError(
              "Error loading base model {} - file not found.".format(
                  fallback_filename
              )
          )
      self.fallback_filename = fallback_filename
      self.fallback_future = self.tpe.submit(
          joblib.load, fallback_filename
      )
      self.fallback_ = None
  
imports: import os
  from concurrent.futures import ThreadPoolExecutor
  import logging
  import sys
  import re
  import joblib
  import numpy
  import tensorflow
  from tensorflow.compat.v1.train import SessionRunHook
  from tensorflow_estimator.python.estimator.early_stopping import _StopOnPredicateHook
  from finetune.errors import FinetuneError
  from finetune.config import get_config
  from finetune.util.metrics import read_eval_metrics
label_desc: Use image node_id 2 for calling the Saver obj's underlying member method code with example usage: obj.set_fallback(fallback_filename) without return types