docs: def save(self, obj):
          """Required functionality."""
          if not obj.id:
              obj.id = uuid()
  
          stored_data = {
              '_id': obj.id,
              'value': json.loads(obj.to_data())
          }
  
          index_vals = obj.indexes() or {}
          for key in obj.__class__.index_names() or []:
              val = index_vals.get(key, '')
              stored_data[key] = str(val)
  
          coll = self.get_collection(obj.__class__.get_table_name())
          coll.update({"_id": obj.id}, stored_data, upsert=True)