def on_close(self, view):

        global LEFT
        vid = view.id()
        if LEFT is not None and vid == LEFT["view_id"]:
            LEFT = None
            update_menu()
value should be a list of role name.
dataset/ETHPy150Open facelessuser/EasyDiff/easy_diff_basic.py/EasyDiffListener.on_close--crossover with--dataset/ETHPy150Open openstack/compass-core/compass/db/models.py/ClusterHost.roles