https://github.com/mozilla/pdf.js/blob/0df1a5661958df0c4ed2f73b0f3266d825c5c280/src/display/api.js#L710-L719
The return type signature `@returns {Promise<{num: number, gen: number}>}` is mismatched with its definition. (should be `@returns {Promise<number>}`)
this.destroyed = true;
      const transportDestroyed = !this._transport
        ? Promise.resolve()
        : this._transport.destroy();
      return transportDestroyed.then(() => {
        this._transport = null;
        if (this._worker) {
          this._worker.destroy();
          this._worker = null;
        }
      });
    }
  }
  return PDFDocumentLoadingTask;
})();
/**
 * Abstract class to support range requests file loading.
 */
class PDFDataRangeTransport {
  /**
   * @param {number} length
   * @param {Uint8Array} initialData
   * @param {boolean} [progressiveDone]
   * @param {string} [contentDispositionFilename]
   */
  constructor(