The standard library and rayon both return concrete types (Enumerate<Self>, Map<Self>, etc. ) from iterator trait functions, rather than impl ParIter, like orx-parallel does.

Refactoring orx-parallel to also return concrete types would be quite a large refactor, but will make use cases like enumeration, where the trait ParEnumerate is not part of ParIter, much more elegant; right now, .enumerate() can only be called immediately after into_par, as it has to be called on the concrete type Par.