code: public void execute() throws DevFailed {
          GroupCmdReplyList replies;
          if (isArginVoid()) {
              replies = group.command_inout(commandName, true);
          } else {
              replies = group.command_inout(commandName, inData, true);
          }
          if (replies.has_failed()) {
              // get data to throw e
              for (final Object obj : replies) {
                  ((GroupCmdReply) obj).get_data();
              }
          }
      }
docs: Execute the command on a single device or on a group If group is used the return data is not managed for the
  moment.
  
  @throws DevFailed