depths = tf.constant(
          np.array([[0.1, 0.2, 0.3, 0.4, 0.5],
                    [float('nan'), 0.7, float('nan'), 0.9, 0.4],
                    [0.4, 0.1, 0.4, 0.2, 0.0],
                    [0.5, 0.0, 7.0, 0.7, 0.4]]),