def to_csv(columns: nil)
      attributes = members
      attributes = columns & attributes if columns

      row = attributes.map! { |column| to_csv_value(column) }

      ::CSV.generate_line(row)
    end
def to_csv(columns: nil)
      attributes = members
      attributes = columns & attributes if columns

      row = attributes.map! { |column| to_csv_value(column) }

      ::CSV.generate_line(row)
    end
Represent row as CSV
 @param columns [Array<Symbol>, Set<Symbol>, NilClass]
   the columns to output, nil means all columns (default: nil)
 @return [String] CSV-string representation.