Get an aggregate of all gauge data stored in the specified date
        range

def aggregate(self, key, aggregate, start=None, end=None,
                  namespace=None, percentile=None):
        """Get an aggregate of all gauge data stored in the specified date
        range"""
        return self.make_context(key=key, aggregate=aggregate, start=start,
                                 end=end, namespace=namespace,
                                 percentile=percentile).aggregate()