code: @CanIgnoreReturnValue
    public <A extends Appendable> A appendTo(A appendable, Iterator<?> parts) throws IOException {
      checkNotNull(appendable);
      if (parts.hasNext()) {
        appendable.append(toString(parts.next()));
        while (parts.hasNext()) {
          appendable.append(separator);
          appendable.append(toString(parts.next()));
        }
      }
      return appendable;
    }
docs: Appends the string representation of each of {@code parts}, using the previously configured
  separator between each, to {@code appendable}.
  
  @since 11.0