message: Reset best weights in EarlyStopping.on_train_begin
  EarlyStopping callback instances can be reused in different training loops, but the `on_train_begin` hook forgets to reset the `self.best_weights` state.
diff: @@ -1524,6 +1524,7 @@ class EarlyStopping(Callback):
  self.best = self.baseline
  else:
  self.best = np.Inf if self.monitor_op == np.less else -np.Inf
  + self.best_weights = None
  def on_epoch_end(self, epoch, logs=None):
  current = self.get_monitor_value(logs)
  