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