def METHOD_NAME(expanded_arguments, assigned_arg, model_type):
    '''
    Return a validator which will aggregate multiple arguments to one complex argument.
    '''
    def _expansion_validator_impl(namespace):
        '''
        The validator create a argument of a given type from a specific set of arguments from CLI
        command.
        :param namespace: The argparse namespace represents the CLI arguments.
        :return: The argument of specific type.
        '''
        ns = vars(namespace)
        kwargs = dict((k, ns[k]) for k in ns if k in set(expanded_arguments))
        setattr(namespace, assigned_arg, model_type(**kwargs))
    return _expansion_validator_impl