Serializes an image/label as a TFExample byte string

def toTFExample(image, label):
  """Serializes an image/label as a TFExample byte string"""
  example = tf.train.Example(
    features=tf.train.Features(
      feature={
        'label': tf.train.Feature(int64_list=tf.train.Int64List(value=label.astype("int64"))),
        'image': tf.train.Feature(int64_list=tf.train.Int64List(value=image.astype("int64")))
      }
    )
  )
  return example.SerializeToString()