code: def add_mutually_exclusive_args(parser, args, required=False, prefix=DATA_PREFIX):
      
      parser = parser.add_mutually_exclusive_group(required=required)
      for arg, kwargs in iteritems(args):
          arg_name = kwargs.pop('arg', arg.replace('_', '-'))
          if 'metavar' not in kwargs:
              kwargs['metavar'] = arg.upper()
          parser.add_argument('--' + arg_name, dest=prefix + arg, **kwargs)
docs: Helper method that populates mutually exclusive arguments. The argument values can
      be later retrieved with `extract_arguments` method.
  
      The `args` argument to this method should be a dict with strings as
      keys and dicts as values. The keys will be used as keys in returned
      data. Their values will be passed as kwargs to `parser.add_argument`.
      There is special value `arg` that will be used as argument name if
      present, otherwise a name will be generated based on the key.
  
      ``required`` will be passed to `parser.add_mutually_exclusive_group` to
      to indicate that at least one of the mutually exclusive arguments is required.