code: public DataSetBuilder set(String column, ColumnFiller<?> filler) {
      ensureArgNotNull(column);
      ensureArgNotNull(filler);
      if (! data.getSource().getDB().isEnabled(DB.Option.CASE_SENSITIVE_COLUMN_NAMES)) {
        column = column.toUpperCase();
      }
      Integer idx = columnIdx.get(column);
      if (idx == null) {
        throw new InvalidOperationException("Invalid column name: '" + column + "'.");
      }
      if (fillers[idx] == null) {
        fillerCount ++;
      }
      fillers[idx] = filler;
      return this;
    }
docs: Set filler for column.
  @param column Column name.
  @param filler Column filler.
  @return The builder instance (for chained calls).