'ResNet constructor.
Args:
hps: Hyperparameters.
images: Batches of images. [batch_size, image_size, image_size, 3]
labels: Batches of labels. [batch_size, num_classes]
mode: One of \'train\' and \'eval\'.'

def __init__(self, hps, images, labels, mode):

    self.hps = hps
    self._images = images
    self.labels = labels
    self.mode = mode
    self._extra_train_ops = []
