def off(hook_type, name = ANY_STATE, &callback)
      sync_exclusive do
        hooks.unregister hook_type, name, callback
      end
    end
def off(hook_type, name = ANY_STATE, &callback)
      sync_exclusive do
        hooks.unregister hook_type, name, callback
      end
    end
Unregister callback for a given event

 @api public