def METHOD_NAME(self):
    if self.cleaned_data.get('meetingtype', None) == MeetingType.WEB and not settings.MEETINGS_WS_BASE_URL:
        raise ValidationError("Web meetings server is not configured in local_settings.py")
    if self.instance and self.instance.state > 0 and self.instance.meetingtype != self.cleaned_data['meetingtype']:
        raise ValidationError("Cannot change the type of a meeting that has already started")
    return self.cleaned_data.get('meetingtype', None)