destroyApp() {
    const pool = this.getConf('pool');
    const render = this.getConf('render');

    if (pool) {
      this.app.destroyChildren(true);
      Pool.put(`${this.type}_${render}`, this.app);
    } else {
      this.app.destroy(true, true);
    }

    if (this.cleanAllCache) destroyAndCleanAllCache();
    this.app = null;
  }
Destroy the App class created by InkPaint
@private