def bestModelInCompletedSprint(self, sprintIdx):
sprintInfo = self._state['<STR_LIT>'][sprintIdx]<EOL>return (sprintInfo['<STR_LIT>'],<EOL>sprintInfo['<STR_LIT>'])<EOL>
Return the best model ID and it's errScore from the given sprint.
        If the sprint has not completed yet, the bestModelID will be None.

        Parameters:
        ---------------------------------------------------------------------
        retval:   (modelId, errScore)