code: def child(self, **kwargs):
          '''set childSelector.'''
          return AutomatorDeviceObject(
              self.device,
              self.selector.clone().child(**kwargs)
          f child(self, **kwargs):
          '''set childSelector.'''
          return AutomatorDeviceObject(
              self.device,
              self.selector.clone().child(**kwargs)
          )
docs: set childSelector.