.done( __ => {
result.total = _.reduce(_.values(result), (sum, n) => money.add(sum, n), money.centsToAmount('0'));
cb(null, result);
});
.each(group => {
result[group[0].expense] = _.reduce(group, (sum, n) => money.add(sum, n.value), money.centsToAmount('0'));
})