code: public static <T> List<T> plus(List<T> self, int index, Iterable<T> additions) {
          return plus(self, index, toList(additions));
      }
docs: Creates a new List by inserting all of the elements in the given Iterable
  to the elements from this List at the specified index.
  
  @param self      an original list
  @param additions an Iterable containing elements to be merged with the elements from the original List
  @param index     index at which to insert the first element from the given additions Iterable
  @return the new list
  @since 1.8.7
  @see #plus(List, int, List)