code: public Object getValue(Object row, int rowIndex, int columnIndex) {
          if (valueModel instanceof NestedValueModel) {
              NestedValueModel nestedModel = (NestedValueModel) valueModel;
              nestedModel.getSourceModel().setValue(row);
          }
          return valueModel.getValue();
      }
docs: Evaluates the value of a cell
  
  @return the value
  @param row the row of interest
  @param rowIndex the index of the row of interest
  @param columnIndex the column of interest