message: Roll back the change to make ModelCheckpoint.epochs_since_last_save attribute private to unbreak tests.
diff: @@ -844,7 +844,7 @@ class ModelCheckpoint(Callback):
  self.save_weights_only = save_weights_only
  self.save_freq = save_freq
  self.load_weights_on_restart = load_weights_on_restart
  - self._epochs_since_last_save = 0
  + self.epochs_since_last_save = 0
  self._samples_seen_since_last_saving = 0
  # Deprecated field `period` is for the number of epochs between which
  @@ -920,7 +920,7 @@ class ModelCheckpoint(Callback):
  self._current_epoch = epoch
  def on_epoch_end(self, epoch, logs=None):
  - self._epochs_since_last_save += 1
  + self.epochs_since_last_save += 1
  if self.save_freq == 'epoch':
  self._save_model(epoch=epoch, logs=logs)
  @@ -943,8 +943,8 @@ class ModelCheckpoint(Callback):
  return
  if isinstance(self.save_freq,
  - int) or self._epochs_since_last_save >= self.period:
  - self._epochs_since_last_save = 0
  + int) or self.epochs_since_last_save >= self.period:
  + self.epochs_since_last_save = 0
  filepath = self.filepath.format(epoch=epoch + 1, **logs)
  if self.save_best_only:
  