I'm trying to define a possibly null property, [as far as I can tell in OpenAPI 3.1 the syntax should be](https://stackoverflow.com/questions/23729973/how-to-specify-a-property-as-null-or-a-reference): ```yaml myData: type: object properties: fooBar: anyOf: - $ref: '#/components/schemas/foos' - type: 'null' ``` This clashes with ibm-schema-type-format which returns an error: ```text Message : Invalid type; valid types are: array, boolean, integer, number, object, string ```