import tensorflow as tf

                         [1, 1, 1, 1, 0, 0, 0, 0]],
                        dtype=tf.float32)
    mask1 = tf.constant([[1, 1, 1, 1, 1, 1, 1, 1],
                         [1, 1, 0, 0, 0, 0, 0, 0],
                         [1, 0, 0, 0, 0, 0, 0, 0],
                         [0, 0, 0, 0, 0, 0, 0, 0],
                         [0, 0, 0, 0, 0, 0, 0, 0]],
                        dtype=tf.float32)
    mask2 = tf.constant([[0, 0, 0, 0, 0, 0, 0, 0],
                         [0, 0, 1, 1, 1, 1, 1, 1],
                         [0, 1, 1, 1, 1, 1, 1, 1],
                         [0, 0, 0, 0, 1, 1, 1, 1],
                         [0, 0, 0, 0, 1, 1, 1, 1]],
                        dtype=tf.float32)
    masks = tf.stack([mask0, mask1, mask2])
    return masks
