code: @Override
      public Response send(String CorpNum, MgtKeyType KeyType, String MgtKey,
                           String Memo) throws PopbillException {
          return send(CorpNum, KeyType, MgtKey, Memo, null);
      }
docs: /* (non-Javadoc)
  @see com.popbill.api.TaxinvoiceService#send(java.lang.String, com.popbill.api.taxinvoice.MgtKeyType, java.lang.String, java.lang.String)