...which then also allow to fill in the missing parts for the
default 1:1 wiring scheme, which connects each »input slot«
of the processing function with the corresponding ''lead node''
...and the nice thing is, the recently built `IterIndex` iteration wrapper
covers this functionality right away, simply because `lib::Several`
is a generic container with subscript operator.
The way I've written this helper template, as a byproduct
it is also possible to maintain the back-refrence to the container
through a smart-ptr. In this case, the iterator-handle also manages
the ownership automatically.
...mostly we want the usual convenient handling pattern for iterators,
but with the proviso actually to perform an access by subscript,
and the ability to re-set to another current index
