FHIR deserialization

I use C# Firely SDK to store documents using the bson serialize/deserialize process. I’m trying to use Python to read those same documents in and put them in the appropriate FHIR resource Class. Using C# it is clear how the mongo driver works - - a document is retrieved and it is deserialized into a class. Using pymongo, I can find something out of a collection.find_one search but I have no idea what it is. I’ve tried several ways to deserialize it into a fhir.resources class and nothing works. How can I get a pymongo returned “thing” into a FHIR resource - - I don’t care what FHIR library I need to use.