docs: def get_controller_by_id(self, id):
          """Get the controller object given the id.
  
          This method returns the controller object for given id.
  
          :param id: id of the controller, for example
              'Smart Array P822 in Slot 2'
          :returns: Controller object which has the id or None if the
              controller is not found.
          """
          for controller in self.controllers:
              if controller.id == id:
                  return controller
          return None