def dump(records, dump = '')
      # each is faster than inject
      records.each do |record|
        record[1] = @serializer.dump(record.last)
        dump << @format.dump(record)
      end
      dump
    end
def dump(records, dump = '')
      # each is faster than inject
      records.each do |record|
        record[1] = @serializer.dump(record.last)
        dump << @format.dump(record)
      end
      dump
    end
Return database dump as string