code: def borrow_optimizer(self, shared_module):
          
          assert shared_module.optimizer_initialized
          self._optimizer = shared_module._optimizer
          self._kvstore = shared_module._kvstore
          self._update_on_kvstore = shared_module._update_on_kvstore
          self._updater = shared_module._updater
          self.optimizer_initialized = True
docs: Borrows optimizer from a shared module. Used in bucketing, where exactly the same
          optimizer (esp. kvstore) is used.
  
          Parameters
          ----------
          shared_module : Module