code: def init_app(self, app):
          
          # Save this so we can use it later in the extension
          if not hasattr(app, 'extensions'):  # pragma: no cover
              app.extensions = {}
          app.extensions['flask-graphql-auth'] = self
  
          self._set_default__configuration_options(app)
docs: Register this extension with the flask app.
  
          :param app: A flask application