Python Decorator validation

I'm using decorators to validate parameters arriving to my function (via a dictionary object), when I have 2 keys or more it works fine. But if I have only key it returns an error (check_person). I defined 2 functions to exemplify my problem:

    def required(**mandatory):
        """

        :param mandatory:
        :return:
        """

        def decorator(f):
            @wraps(f)
            def wrapper(**dicts):
                for argname, d in dicts.items():
                    for key in mandatory.get(argname, []):
                        if key not in d:
                            raise Exception('Key "%s" is missing from argument "%s"' % (key, argname))
                return f(**dicts)
            return wrapper
        return decorator

@required(json_request=(_PROVIDER, _REPORT))
def check_campaign(json_request):
    """

    :param json_request:
    :return:
    """

    return True

@required(json_request=(_NAME))
def check_person(json_request=None):
    """

    :param json_request:
    :return:
    """
    return True

I need to change check_person to:

if _NAME in json_request:
        return True
    return False

To make it work.

When I try:

self.assertTrue(validator.check_person(json_request=json.loads("""{"name": "Elon Musk"}""")))

or specifically:

{"name": "Elon Musk"}

I get:

Error
Traceback (most recent call last):
  File "/Users/spicyramen/Documents/OpenSource/Development/Python/gonzo/utils/validate/validator_test.py", line 46, in test_person
    self.assertTrue(validator.check_person(json_request=json.loads("""{"name": "Elon Musk"}""")))
  File "/Users/spicyramen/Documents/OpenSource/Development/Python/gonzo/utils/validate/validator.py", line 26, in wrapper
    raise Exception('Key "%s" is missing from argument "%s"' % (key, argname))
Exception: Key "n" is missing from argument "json_request"

When my dictionary has more than 1 key it works fine (Like check_campaign).