mapIndexedTo<R, C extends KtMutableCollection<R> >  method 
Applies the given transform function to each element and its index in the original collection
and appends the results to the given destination.
@param transform function that takes the index of an element and the element itself
and returns the result of the transform applied to the element.
Implementation
C mapIndexedTo<R, C extends KtMutableCollection<R>>(
    C destination, R Function(int index, T) transform) {
  var index = 0;
  for (final item in iter) {
    destination.add(transform(index++, item));
  }
  return destination;
}