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>}`)
sink.enqueue(new Uint8Array(value), 1, [value]);
          })
          .catch(reason => {
            sink.error(reason);
          });
      };
      sink.onCancel = reason => {
        this._fullReader.cancel(reason);
        sink.ready.catch(readyReason => {
          if (this.destroyed) {
            return; 
          }
          throw readyReason;
        });
      };
    });
    messageHandler.on("ReaderHeadersReady", data => {
      const headersCapability = createPromiseCapability();
      const fullReader = this._fullReader;
      fullReader.headersReady.then(() => {
        
        
        if (!fullReader.isStreamingSupported || !fullReader.isRangeSupported) {
          if (this._lastProgress && loadingTask.onProgress) {
            loadingTask.onProgress(this._lastProgress);
          }
          fullReader.onProgress = evt => {
            if (loadingTask.onProgress) {