human
I wrote the below code

    app = QApplication(sys.argv)
    signal.signal(signal.SIGINT, signal.SIG_DFL)
    class MyQWebPage(QWebPage, ):
        @pyqtSlot()
        def shouldInterruptJavaScript(qwebpage):
            print 'not    interrupting'
            return False
    webpage = MyQWebPage()
    webpage.setViewportSize(QSize(int(width), int(height)))
    def print_error(message, lineNumber, sourceID):
        print ('\n%(sourceID)s    line    %(lineNumber)i:    \n        %(message)s' % locals())
    webpage.javaScriptConsoleMessage = print_error
    if (file_name is None):
        result = []
    def onPrintRequested(virtual_browser_window):
        image = QImage(webpage.viewportSize(), QImage.Format_ARGB32)
        painter = QPainter(image)
        virtual_browser_window.render(painter)
        painter.end()
        if (file_name is not None):
            image.save(file_name)
        else:
            byte_array = QByteArray()
            buffer = QBuffer(byte_array)
            buffer.open(QIODevice.WriteOnly)
            image.save(buffer, 'PNG')
            result.append(str(byte_array))
        if (__name__ == '__main__'):
            if (file_name is None):
                sys.stdout.write(result[0])
            sys.exit(0)
        else:
            app.quit()
    webpage.printRequested.connect(onPrintRequested)
    webpage.mainFrame().load(QUrl(url))
    app.exec_()
    if (file_name is None):
        return result[0]

What's a good function header?
 Can you provide a Python code to print 'not    interrupting'?
assistant
#Here is Python code to print 'not    interrupting'
.

def save_webpage_screenshot(url, width, height, file_name=None):