How to connect PDF.js rendering signal to PyQt5.QtWebEngineWidgets

Question

I use PyQt5.QtWebEngineWidgets with PDF.js to display pdf files. Is it possible to connect the rendering state of the page to the PyQt5.QtWebEngineWidgets, so that another function is run, when rendering is complete?

Edit:

I tried different solutions, e.g. the solution given here. Unfortunately I can't find a solution how to connect the solutions described there with my PyQt5.QWebEngineView.

The way I tried: I added a new class function called rendering_state to my QWebEngineView. When the rendering is done (solution from here), I want get the notification that the rendering is complete so that I can later insert another function there. Unfortunately, I don't get an notification, I only get the warning js: Uncaught ReferenceError: renderContext is not defined. I just don't know from where I get the renderContext variable

The function I added is this:

def rendering_state(self):
    js_script = """
                    var page = PDFViewerApplication.pdfViewer.currentPageNumber;
                    //Step 1: store a refer to the renderer
                    var pageRendering = page.render(renderContext);
                    //Step : hook into the pdf render complete event
                    var completeCallback = pageRendering.internalRenderTask.callback;
                    pageRendering.internalRenderTask.callback = function (error) {
                    //Step 2: what you want to do before calling the complete method                  
                    completeCallback.call(this, error);
                    //Step 3: do some more stuff
                    alert("done");
                    };
    """
    self.page().runJavaScript(js_script)

I run the function on my QWebEngineView like this:

webView = MyWebView()
webView.load(QUrl.fromUserInput('%s?file=%s' % (PDFJS, PDF)))
webView.rendering_state()

Is it the right approach to add a class function and run, after QWebEngineView is initiated?