code: public void addValue(final Instance _rowInstance,
                           final UIFieldSetValue _uiFieldSetValue)
      {
          this.instKey2row.get(_rowInstance.getKey()).add(_uiFieldSetValue);
      }
docs: Adds the value.
  
  @param _rowInstance instance for the row to be added
  @param _uiFieldSetValue the _ui field set value