def update(self, instance_id: str, details: UpdateDetails, async_allowed: bool) -> UpdateServiceSpec:
        """
        Further readings `CF Broker API#Update <https://docs.cloudfoundry.org/services/api.html#updating_service_instance>`_

        :param instance_id: Instance id provided by the platform
        :param details: Details about the service to update
        :param async_allowed: Client allows async creation
        :rtype: UpdateServiceSpec
        :raises ErrAsyncRequired: If async is required but not supported
        """
        raise NotImplementedError()
Further readings `CF Broker API#Update <https://docs.cloudfoundry.org/services/api.html#updating_service_instance>`_

        :param instance_id: Instance id provided by the platform
        :param details: Details about the service to update
        :param async_allowed: Client allows async creation
        :rtype: UpdateServiceSpec
        :raises ErrAsyncRequired: If async is required but not supported