code: public OrderBy add(String name, Order order) {
      failIfFieldNamePresent(name);
      this.elements.add(new SortElement(name, order, NullOrder.NULL_SMALLEST));
      return this;
    }
docs: Adds a new field to order by and its specified order.
  <br/>
  The default @{link NullOrder} used is for nullable fields is @{link NullOrder#NULL_SMALLEST}
  
  @param name  Field's name
  @param order Field's order
  @see Order