Check that output indices are stored
The c++ algorithm std::is_sorted is marked with the attribute nodiscard. The result of the check that the output indexset is sorted is currently lost. This MR wraps this check in an if-not-then-throw block.
The c++ algorithm std::is_sorted is marked with the attribute nodiscard. The result of the check that the output indexset is sorted is currently lost. This MR wraps this check in an if-not-then-throw block.
