code: def add_flag(*args, **kwargs):
      
      if len(args) == 1 and isinstance(args[0], (list, tuple)):
          for a in args[0]:
              flag.add_flag(*a)
      elif args:
          flag.add_flag(*args, **kwargs)
      else:
          for f, v in kwargs.items():
              flag.add_flag(f, v)
docs: define a single flag.
      add_flag(flagname, default_value, help='', **kwargs)
      add_flag([(flagname, default_value, help), ...])
      or
      define flags without help message
      add_flag(flagname, default_value, help='', **kwargs)
  
      add_flag('gpu', 1, help='CUDA_VISIBLE_DEVICES')
      :param args:
      :param kwargs:
      :return: