def set_checksums
      @sum_bank_account_numbers, @sum_bank_numbers, @sum_values  = 0,0,0
      bookings.each do |b|
        @sum_bank_account_numbers  += b.account.bank_account_number
        @sum_bank_numbers += b.account.bank_number
        @sum_values += b.value
      end
    end
def set_checksums
      @sum_bank_account_numbers, @sum_bank_numbers, @sum_values  = 0,0,0
      bookings.each do |b|
        @sum_bank_account_numbers  += b.account.bank_account_number
        @sum_bank_numbers += b.account.bank_number
        @sum_values += b.value
      end
    end
TODO do it works? the .to_i stuff