Returns the total sum of data as it grows with series.
The cumulative total of salaries by departments:
{d.departments[i].people[].salary:cumSum}
{d.departments[i+1]}
The cumulative total of salaries by departments and by people:
{d.departments[i].people[i].salary:cumSum}
{d.departments[i+1].people[i+1]}
The cumulative total of salaries by departments: 1000 1700 3200 3400
The cumulative total of salaries by departments and by people: 1000 1500 1700 3200 3400