get(key, options) {
    const entry = this.entries_[key];
    assert(
      entry !== undefined,
      'Tried to get a value for a key that does not exist in the cache',
    );
    if (entry === this.newest_) {
      return entry.value_;
    }
    if (entry === this.oldest_) {
      this.oldest_ = /** @type {Entry} */ (this.oldest_.newer);
      this.oldest_.older = null;
    } else {
      entry.newer.older = entry.older;
      entry.older.newer = entry.newer;
    }
    entry.newer = null;
    entry.older = this.newest_;
    this.newest_.newer = entry;
    this.newest_ = entry;
    return entry.value_;
  }
@param {string} key Key.
@param {*} [options] Options (reserved for subclasses).
@return {T} Value.