code: def get_one(self, key):
          
          query = {'_id': ObjectId(key)}
          collection = self.ds.connection(COLLECTION_UNIT_OF_WORK)
  
          document = collection.find_one(query)
          if document is None:
              msg = 'UOW with ID={0} was not found'.format(key)
              self.logger.warning(msg)
              raise LookupError(msg)
          return UnitOfWork.from_json(document)
docs: method finds unit_of_work record and returns it to the caller