code: public Vector list(String filter, String modifier)
          throws ServerException, ClientException, IOException {
          if (gSession.parallel > 1) {
              throw new ClientException(
                        ClientException.BAD_MODE,
                        "list cannot be called with parallelism");
          }
          return super.list(filter, modifier);
      }
docs: Performs remote directory listing like
  {@link FTPClient#list(String,String) FTPClient.list()}.
  <b>Note:</b> This method cannot be used
  in conjunction with parallelism or striping; set parallelism to
  1 before calling it. Otherwise, use
  {@link FTPClient#list(String,String,DataSink) FTPClient.list()}.
  Unlike in vanilla FTP, here IMAGE mode is allowed.
  For more documentation, look at FTPClient.