code: def retrieve(self, request, _id):
          
          _id = deserialize(_id)
  
          retrieved = self.collection.find_one({'_id': _id})
          if retrieved:
              return Response(serialize(retrieved))
          else:
              return Response(
                  response=serialize(
                      DocumentNotFoundError(self.collection.__name__, _id)
                  ),
                  status=400
              )
docs: Returns the document containing the given _id or 404