@SafeVarargs
  @Contract(pure = true)
  public static @NotNull <T> Iterator<T> concatIterators(@NotNull Iterator<? extends T> @NotNull ... iterators) {
    return new SequenceIterator<>(iterators);
  }
@SafeVarargs
  @Contract(pure = true)
  public static @NotNull <T> Iterator<T> concatIterators(@NotNull Iterator<? extends T> @NotNull ... iterators)