def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def handleevent(self):
        """
        Event-handler for the 'widgets' demo
        """
        while True:
            event = self.dialog.waitForEvent()
            if event.eventType() == yui.YEvent.CancelEvent:
                self.dialog.destroy()
                break
            if event.widget() == self.closebutton:
                info = Info("Quit confirmation", 1, "Are you sure you want to quit?")
                if self.ask_YesOrNo(info):
                    self.dialog.destroy()
                    break
            if event.widget() == self.aboutbutton:
                self.aboutDialog()