message: Use python2-compatible matmul
diff: @@ -74,7 +74,8 @@ x
  # [ 2.6666665 ],
  # [-1.3333331 ]], dtype=float32)>
  -a@x
  +# in python3 one can use `a@x`
  +tf.matmul(a, x)
  # <tf.Tensor: id=263, shape=(4, 1), dtype=float32, numpy=
  # array([[4. ],
  # [2. ],
  