docs: public void add(Block key, Block value, int keyPosition, int valuePosition)
      {
          if (!keyExists(key, keyPosition)) {
              addKey(key, keyPosition);
              if (value.isNull(valuePosition)) {
                  valueBlockBuilder.appendNull();
              }
              else {
                  valueType.appendTo(value, valuePosition, valueBlockBuilder);
              }
          }
      }