[batch] add close method to Backend (#9191)
[batch] add close method to Backend (#9191)

* add close

* fix

* fix

* fix

* main switch errors

* group imports
hail-is/hail,cseed/hail,hail-is/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail,cseed/hail,danking/hail,danking/hail,hail-is/hail,cseed/hail,cseed/hail,danking/hail,hail-is/hail,cseed/hail,cseed/hail,cseed/hail,danking/hail