'Increment project ID=1 and group ID=5:
>>> incr_multi([(TimeSeriesModel.project, 1), (TimeSeriesModel.group, 5)])'

def incr_multi(self, items, timestamp=None, count=1):

    make_key = self.make_counter_key
    normalize_to_rollup = self.normalize_to_rollup
    if (timestamp is None):
        timestamp = timezone.now()
    with self.cluster.map() as client:
        for (rollup, max_values) in six.iteritems(self.rollups):
            norm_rollup = normalize_to_rollup(timestamp, rollup)
            for (model, key) in items:
                model_key = self.get_model_key(key)
                hash_key = make_key(model, norm_rollup, model_key)
                client.hincrby(hash_key, model_key, count)
                client.expireat(hash_key, self.calculate_expiry(rollup, max_values, timestamp))
