(stdDevSamp: StringAdd).self
(stdDevSamp: StringFormat).self
(stdDevSamp: ArrowAssoc[AggregationFramework.StdDevSamp]).x
(Since version 2.10.0) Use leftOfArrow
instead
(stdDevSamp: Ensuring[AggregationFramework.StdDevSamp]).x
(Since version 2.10.0) Use resultOfEnsuring
instead
The $stdDevSamp group accumulator (since MongoDB 3.2)