The MONAO dict-based transforms acts on the top level keys, for instance data={"image": ..., "pred": ...}; however, when the output is nested (like in the hovernet model), the actual data will lie one level below like data={"image": ..., "pred": {"a":..., "b":...}}.

Currently, if user want to apply transform on "a" or "b", it can use Lambdad and apply that transfrom on data["pred"] instead and use "a" and "b" as keys. However, if the user want to apply a transform on "image" and "a" for instance, I didn't find any transform that can enable it.

Here a transform that can promote these children items ("a" and "b") to the same level of "image" can solve the problem.