Dynamic property types in Swagger Specification

Question

Is it possible to define properties in a Swagger/OpenAPI definition that can be one of two types.

For example, our API allows a source ID to be sent as a string, or a source object. The source object has a fixed schema:

Source ID:

{
    "source": "src_123"
}

Source Object:

{
    "source": {
        "foo": "bar"
    }
}

I am unsure how to represent this in my Swagger definition.