JsonifyObject

type JsonifyObject<BaseType, Marker extends string> = {
    [
        K in keyof BaseType as K extends symbol
            ? never
            : BaseType[K] extends (
                    ...args: unknown[]
                ) => unknown
              ? never
              : K
    ]:
        | JsonifyWithCirculars<
              Exclude<BaseType[K], undefined>,
              Marker
          >
        | Extract<BaseType[K], undefined>
        | Marker;
};