code: public void updateColumnMappings() {
          columnMapping = new HashMap<>();
          int realIdx = 0;
          int renderCol = 0;
          for (final SheetColumn column : getColumns()) {
              if (column.isRendered()) {
                  columnMapping.put(renderCol, realIdx);
                  renderCol++;
              }
              realIdx++;
          }
      }
docs: Updates the column mappings based on the rendered attribute