[Python] Can't figure out why json-schema validation not working with recursive defs

I've simplified this to make it easier to convey, but I have a yaml I parse using PyYaml and then I want to validate it against a json-schema. I'm struggling to figure out why validation is failing against my schema when I go more than one level deep. I'm using validate from jsonschema package

Sample YAML:

TOP_LEVEL_KEY:
first_level:
can_be_any_value:
some_setting: value
second_level:
any_value:
some_setting: value2

SOME_OTHER_TOP_LEVEL:
....


first_level and second_level are predefined to some Enum list. There can be indeterminate number of levels.

Schema:

yaml_schema = {
'$defs': {
'ConfigLevel': {
'type': 'object',
'propertyNames': {
'enum': [
'first_level',
'second_level',
]
},
"additionalProperties": {
'type': 'object', # the 'can_by_any_value' objects
"additionalProperties": {
'type': 'object',
'properties': {
'some_setting': {
'type': 'string'
},
},
"additionalProperties": {
'$ref': '#/$defs/ConfigLevel'
}
}
}
}
},
'type': 'object',
'additionalProperties': {
'$ref': '#/$defs/ConfigLevel'
}
}


Sample as written will fail with:

jsonschema.exceptions.ValidationError: 'can_by_any_value' is not one of ['first_level', 'second_level']


But this YAML will validate

TOP_LEVEL_KEY:
first_level:
can_be_any_value:
some_setting: value
second_level:
any_value:
some_setting: value2



So the issue is when the recursive definition in the additionalProperties with the #/$defs/ConfigLevel but I've simplified it as far as I can go and am stuck.

Sample PyTest:

import pytest
import yaml
from jsonschema import validate

@pytest.fixture(scope="module")
def yaml_fixture() -> str:
return """
TOP_LEVEL:
first_level:
can_be_any_value:
some_setting: value
second_level:
can_by_any_value:
some_setting: value2
"""

def test_validate_yaml(yaml_fixture):
validate(yaml.safe_load(yaml_fixture), yaml_schema)

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