code: @TimerJ
      public IndexMetadataBuilder addColumn(String columnName, ColumnType colType) {
          ColumnName colName = new ColumnName(tableName, columnName);
          ColumnMetadata colMetadata = new ColumnMetadata(colName, null, colType);
          columns.put(colName, colMetadata);
          return this;
      }
docs: Add column. Parameters in columnMetadata will be null.
  
  @param columnName the column name
  @param colType    the col type
  @return the index metadata builder