python petsird generator produce non-sym. module_pair_SGID_LUT

[MaxTousss]

In #52, a non sym. was highlighted.

It seems that the current petsird generator does not create a case where the scanner has angle sym., right? If that is the case, should we correct it? Currently, it uses abs(a1-a2) to defined "angle distance" but that doesn't work when the shortest "angle" between a1 and a2 is a warp around (e.g., NUM_MODULES_ALONG_RING= 20, a1= 19, a2=1 -> angle should be 2, not 18).

If we also want axial sym., the formula seems to be:
min(z1, z2) + NZ * (max(z2, z1) + NZ * ((a2 - a1) % (NUM_MODULES_ALONG_RING // 2))

[KrisThielemans]

We need to think more about this given #138 (comment)