Why can't I return shared entities of dimension 0 using MeshTopology?

Question

In parallel, I can print the shared nodes by inspecting the dofmap through the following:

const std::unordered_map<int, std::vector>& shared_nodes = dofmap->shared_nodes();

However, when I try to use MeshTopology to find the shared nodes through:

std::map>& shared_entities = MeshTopology().shared_entities(0);

I get nothing, and in fact,

bool bb = MeshTopology().have_shared_entities(0);

returns false.

Note: This is coming up, because I actually want to find the shared faces which are only available through the MeshTopology class.