docs: @Nonnull
      public static <T> List<T> filter( @Nonnull Iterable<?> base, @Nonnull Class<T> type ) {
          List<T> r = new ArrayList<>();
          for (Object i : base) {
              if(type.isInstance(i))
                  r.add(type.cast(i));
          }
          return r;
      }