code: def py_func_grad(func, inp, Tout, stateful=True, name=None, grad=None):
    
    # Need to generate a unique name to avoid duplicates:
    rnd_name = 'PyFuncGrad' + str(np.random.randint(0, 1E+8))
  
    tf.RegisterGradient(rnd_name)(grad)
    g = tf.get_default_graph()
    with g.gradient_override_map({"PyFunc": rnd_name,
                                  "PyFuncStateless": rnd_name}):
      return tf.py_func(func, inp, Tout, stateful=stateful, name=name)
docs: Custom py_func with gradient support