code: public static <T, K, V, M extends Map<K, V>> M addToMap(
              Iterable<T> iterable,
              Function<? super T, ? extends K> keyFunction,
              M map)
      {
          Iterate.forEach(iterable, new MapCollectProcedure<T, K, V>(map, keyFunction));
          return map;
      }
docs: Iterate over the specified collection applying a specific Function to each element to calculate a
  key, and add the results to input Map.
  This method will mutate the input Map.