How to use the voila.app.Voila function in voila

def initialize(self, argv=None):
        self.log.debug("Searching path %s for config files", self.config_file_paths)
        # to make config_file_paths settable via cmd line, we first need to parse it
        super(Voila, self).initialize(argv)
        if len(self.extra_args) == 1:
            arg = self.extra_args[0]
            # I am not sure why we need to check if self.notebook_path is set, can we get rid of this?
            if not self.notebook_path:
                if os.path.isdir(arg):
                    self.root_dir = arg
                elif os.path.isfile(arg):
                    self.notebook_path = arg
                else:
                    raise ValueError('argument is neither a file nor a directory: %r' % arg)
        elif len(self.extra_args) != 0:
            raise ValueError('provided more than 1 argument: %r' % self.extra_args)

        # then we load the config
        self.load_config_file('voila', path=self.config_file_paths)
        # common configuration options between the server extension and the application