random rotate of images is not really random

in bob.learn.tensorflow/bob/learn/tensorflow/dataset/__init__.py there is:

    if random_rotate:
        image = tf.contrib.image.rotate(
            image,
            angles=numpy.random.randint(-5, 5),
            interpolation="BILINEAR")

this random number (from numpy) is going to be evaluated once and then all images will be rotated using that angle.