Initialize the app with Swagger plugin

def init_app(self, app, decorators=None):
        """
        Initialize the app with Swagger plugin
        """
        self.decorators = decorators or self.decorators
        self.app = app

        self.load_config(app)
        # self.load_apispec(app)
        if self.template_file is not None:
            self.template = self.load_swagger_file(self.template_file)
        self.register_views(app)
        self.add_headers(app)

        if self.parse:
            if RequestParser is None:
                raise RuntimeError('Please install flask_restful')
            self.parsers = {}
            self.schemas = {}
            self.format_checker = jsonschema.FormatChecker()
            self.parse_request(app)

        self._configured = True
        app.swag = self