Created by: qingqing01

• Add ProgressBar
• Add callback
• Add fit

callback example:

class ModelCheckpoint(Callback):
    def __init__(self, save_freq=1, save_file='output'):
        self.save_freq = save_freq
        self.save_file = save_file

    def on_epoch_begin(self, epoch=None, logs=None):
        self.epoch = epoch

    def on_epoch_end(self, step, logs=None):
        if self.model and self.epoch % self.save_freq == 0:
            path = '{}/{}'.format(self.save_file, step)
            print('save checkpoint at {}'.format(path))
            self.model.save(path)

    def on_train_end(self, logs=None):
        if self.model:
            path = '{}/final'.format(self.save_file)
            print('save checkpoint at {}'.format(path))
            self.model.save(path)