message: add a warning in ModelCheckpoint callback in case of multi-worker training, to notify user to use BackupAndRestore callback for FT.
diff: @@ -1221,6 +1221,16 @@ class ModelCheckpoint(Callback):
  self.save_weights_only = True
  def on_train_begin(self, logs=None):
  + # pylint: disable=protected-access
  + if self.model._in_multi_worker_mode:
  + logging.warning(
  + 'Automatic model reloading for interrupted job was removed from '
  + 'the `ModelCheckpoint` callback in multi-worker mode, please use the '
  + '`keras.callbacks.experimental.BackupAndRestore` callback instead. '
  + 'See this tutorial for details: '
  + 'https://www.tensorflow.org/tutorials/distribute/'
  + 'multi_worker_with_keras#backupandrestore_callback.'
  + )
  if self.load_weights_on_restart:
  filepath_to_load = (
  self._get_most_recently_modified_file_matching_pattern(self.filepath))
  