How to get all MaterialGroups of a model ?

[gsohler]

I tried to read all BaseMaterialGroups when importing a 3MF Model

I tried this:

Lib3MF::PBaseMaterialGroupIterator basematerial_it = model->GetBaseMaterialGroups();
while (true) {
  if(!basematerial_it->MoveNext()) break;
  std::shared_ptr<Lib3MF::CResource> cr = basematerial_it->GetCurrent();
  std::shared_ptr<Lib3MF::CBaseMaterialGroup> mat = std::dynamic_pointer_cast<Lib3MF::CBaseMaterialGroup>(cr);
  if(mat != nullptr) {
      cout << "worked\n";
  } else cout << "Pointer cast not working\n";
}  

However, the dynamic_pointer_cast does not work even though, reading the header file, CBaseMaterialGroup
is derived from CResource ?

So whats wrong in my strategy ?
How can I get all MaterialGroups ?

class CBaseMaterialGroup : public CResource