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>}`)
font.data = null;
              }
              this.commonObjs.resolve(id, font);
            });
          break;
        case "FontPath":
        case "Image":
          this.commonObjs.resolve(id, exportedData);
          break;
        default:
          throw new Error(`Got unknown common object type ${type}`);
      }
    });
    messageHandler.on("obj", data => {
      if (this.destroyed) {
        
        return undefined;
      }
      const [id, pageIndex, type, imageData] = data;
      const pageProxy = this.pageCache[pageIndex];
      if (pageProxy.objs.has(id)) {
        return undefined;
      }
      switch (type) {
        case "Image":
          pageProxy.objs.resolve(id, imageData);