code: @Override
      public void unset(String propName) {
          if (propName.equals("size")) {
              unsetSize();
          }
          if (propName.equals("startIndex")) {
              unsetStartIndex();
          }
          super.unset(propName);
      }
docs: Sets the value of provided property to null.
  
  @param propName
  allowed object is {@link String}