Method getId

src/data/SeriesData.ts:758–760

* @return Never null/undefined. `number` will be converted to string. Because: * In all cases having encountered at present, id is used in making diff comparison, which * are usually based on hash map. We can keep the rule that the internal id are always string * (treat `2` is the sam

(idx: number)

     * (treat `2` is the same as `'2'`) to make the related logic simple.
     */
    getId(idx: number): string {
        return getId(this, this.getRawIndex(idx));
    }

    count(): number {
        return this._store.count();