code: def test_reduce_on_plateau_works_when_metrics_exist(self):
      model = torch.nn.Sequential(torch.nn.Linear(10, 10))
      LearningRateScheduler.from_params(
          Optimizer.from_params(
              model.named_parameters(), Params({"type": "adam"})
          ),
          Params({"type": "reduce_on_plateau"}),
      ).step(10, None)
  
file_path: magnitude/pymagnitude/third_party/allennlp/tests/training/learning_rate_schedulers_test.py
imports: from __future__ import with_statement
  from __future__ import absolute_import
  import torch
  from allennlp.common.checks import ConfigurationError
  from allennlp.training.optimizers import Optimizer
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.training.learning_rate_schedulers import LearningRateScheduler
  from allennlp.common.params import Params
label_desc: Use image node_id 2 for calling the LearningRateSchedulersTest obj's underlying member method code with example usage: obj.test_reduce_on_plateau_works_when_metrics_exist() without return types