code: @SuppressWarnings("unchecked")
      @Override
      public String execute() {
          User sfsUser = CommandUtil.getSfsUser(username, api);
          return (sfsUser == null) ? "" : sfsUser.getIpAddress();
      }
docs: /* (non-Javadoc)
  @see com.tvd12.ezyfox.core.command.BaseCommand#execute()