Illustration for laplacian indices

[liluo2]

Hi! That's a really brilliant work!
But as I tried to read the code, I found those calculating laplacian indices hard for me to understand... I don't know if there's a illustration or documentation for the code in laplace.py?

For example, I don't understand line 375 of laplace.py:
non_diag_row_indices = (row_template + total_d*row.unsqueeze(1)).reshape(1, -1)

Looking forward to your reply!