Fix HyperparamOpt for Keras models

        model_params[hyperparam] = hyperparam_val

      model_dir = tempfile.mkdtemp()

      model = self.model_class(self.task_types, model_params, logdir=logdir,

                               train=True)

      if not logdir:

        model = self.model_class(self.task_types, model_params)

      else:

        model = self.model_class(self.task_types, model_params, logdir=logdir)

      model.fit(train_dataset)

      model.save(model_dir)