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