PyTorch error isDifferentiableType(variable.scalar_type()) for calculating det of a complex matrix

Question

Following up this post When I want to use complex_det function to calculate det of a complex matrix I face this error:

RuntimeError: isDifferentiableType(variable.scalar_type()) INTERNAL ASSERT FAILED at "/pytorch/torch/csrc/autograd/functions/utils.h":59, please report a bug to PyTorch. 

any idea how I can fix it?

<ipython-input-76-246d142f8871> in complex_det(A)
      3         return torch.view_as_complex(torch.stack((A.real.diag(), A.imag.diag()),dim=1))
      4     #Perform LU decomposition to matrix A:
----> 5     A_LU, pivots = A.lu()
      6     P, A_L, A_U = torch.lu_unpack(A_LU, pivots)
      7     #Det. of multiplied matrices is multiplcation of det.:

/usr/local/lib/python3.6/dist-packages/torch/tensor.py in lu(self, pivot, get_infos)
    332         r"""See :func:`torch.lu`"""
    333         # If get_infos is True, then we don't need to check for errors and vice versa
--> 334         LU, pivots, infos = torch._lu_with_info(self, pivot=pivot, check_errors=(not get_infos))
    335         if get_infos:
    336             return LU, pivots, infos