If I do something along the lines of:

pet.AcquisitionData.set_storage_scheme("file")
a = pet.AcquisitionData(fname1)
pet.AcquisitionData.set_storage_scheme("memory")
b = pet.AcquisitionData(fname2)
print(a.get_storage_scheme())

Despite the fact that a uses file as its storage scheme, the printed output will be memory. This is because the storage scheme is a static variable.

It seems to me that it would be safer to set the storage scheme for each AcquisitionData individually. It can default to file, since this is the current default. Could look like this:

a = pet.AcquisitionData(fname, scheme="file")

If we do not like this, then at the very least, we need to change get_storage_scheme so that it is no longer static and returns its own storage scheme. This could be done by dynamically casting to ProjDataInMemory, and returning the value of is_null_ptr.