angular-ui-bootstrap手风琴折叠/展开全部

I would like to create a collpase/expand all button for a set of accordions. I am using angular.js v1.2.6 and angular-bootstrap-ui 0.9.0. I haven't been able to find an example of how to do a collpase/expand all. I'm an angular novice and any advice or suggestions is appreciated.I would like to create a collpase/expand all bu