What is the best way to validate a dict where the keys are unknown but the values have a definite schema. For example:
data = {
'name': 'test',
'department': {
    'unknown_key': {
        'known_key': 'good',
        'unknown_key': 'bad'
    }
}}
I've tried
schema = {
'name': {
    'type': 'string'
},
'department': {
    'type': 'dict',
    'allow_unknown': {
        'schema': {
            'type': 'dict',
            'schema': {'known_key': {'type': 'string'},
                       'must_have_key': {'type': 'string'}}}
    },
}}
But this has failed as the validation passes. It should have failed on both the missing must_have_key and the unknown_key. Have I defined something wrong?