My question is: which parts of a code I should modify to add internal property maps of custom type? Is it possible without ground-breaking modifications, or should I look a way for some workaround?

My usecase is to bridge python integer objects and big integer objects (from intx library) on c++ side, as a vertex property. I'm going to perform relatively heavy math operations and graph operations, so I want to write a C++ extension that does it.
So I thought, is it possible to add custom property map handlers for big integers, that will convert python long objects to intx type and store it in that type later.