Private method to patch an ISO datetime string to a datetime object
        for metadata key mk.

        :param res: results dict
        :param mk: metadata key

def _patchDatetimeMetadata( self, res, mk ):
        """Private method to patch an ISO datetime string to a datetime object
        for metadata key mk.

        :param res: results dict
        :param mk: metadata key"""
        t = res[epyc.Experiment.METADATA][mk]
        res[epyc.Experiment.METADATA][mk] = dateutil.parser.parse(t)