dump() {
        const arr = [];
        for (const i of this.#indexes({ allowStale: true })) {
            const key = this.#keyList[i];
            const v = this.#valList[i];
            const value = this.#isBackgroundFetch(v)
                ? v.__staleWhileFetching
                : v;
            if (value === undefined || key === undefined)
                continue;
            const entry = { value };
            if (this.#ttls && this.#starts) {
                entry.ttl = this.#ttls[i];
                // always dump the start relative to a portable timestamp
                // it's ok for this to be a bit slow, it's a rare operation.
                const age = perf.now() - this.#starts[i];
                entry.start = Math.floor(Date.now() - age);
            }
            if (this.#sizes) {
                entry.size = this.#sizes[i];
            }
            arr.unshift([key, entry]);
        }
        return arr;
    }
Return an array of [key, {@link LRUCache.Entry}] tuples which can be
passed to cache.load()