pyopencl error in excersises 07 solution

[godcrying]

when I run the python version solution of exercise 07, then I get an error message as follow:

Traceback (most recent call last):
  File "matmul.py", line 111, in <module>
    mmul(queue, (N,), (ORDER/16,), N, d_a, d_b, d_c)
  File "/home/xxx/.local/lib/python3.8/site-packages/pyopencl/__init__.py", line 840, in kernel_call
    return self._enqueue(self, queue, global_size, local_size, *args, **kwargs)
  File "<generated code>", line 74, in enqueue_knl_mmul
RuntimeError: Unable to cast Python instance to C++ type (compile in debug mode for details)

the C language version solution works just fine.