See [opString](https://github.com/scijava/incubator/blob/7f6f07c31198ee7eb25ea02d954cd7deff0e2341/scijava/scijava-ops-api/src/main/java/org/scijava/ops/api/OpInfo.java#L133) - [x] add question mark on optional params - [x] List containers once and not in both inputs/outputs
See opString