static unsafeExposeInternals(c) {
        return {
            // properties
            starts: c.#starts,
            ttls: c.#ttls,
            sizes: c.#sizes,
            keyMap: c.#keyMap,
            keyList: c.#keyList,
            valList: c.#valList,
            next: c.#next,
            prev: c.#prev,
            get head() {
                return c.#head;
            },
            get tail() {
                return c.#tail;
            },
            free: c.#free,
            // methods
            isBackgroundFetch: (p) => c.#isBackgroundFetch(p),
            backgroundFetch: (k, index, options, context) => c.#backgroundFetch(k, index, options, context),
            moveToTail: (index) => c.#moveToTail(index),
            indexes: (options) => c.#indexes(options),
            rindexes: (options) => c.#rindexes(options),
            isStale: (index) => c.#isStale(index),
        };
    }
Do not call this method unless you need to inspect the
inner workings of the cache.  If anything returned by this
object is modified in any way, strange breakage may occur.

These fields are private for a reason!

@internal