def get_one(self, process_name, timeperiod):
        """ method finds a single job record and returns it to the caller"""
        collection_name = self._get_job_collection_name(process_name)
        collection = self.ds.connection(collection_name)
        document = collection.find_one({job.PROCESS_NAME: process_name, job.TIMEPERIOD: timeperiod})

        if document is None:
            raise LookupError('MongoDB has no job record in collection {0} for {1}@{2}'
                              .format(collection, process_name, timeperiod))
        return Job.from_json(document)