code: def test_lambda_lr(self, lr_mock):
      state = {
          torchbearer.OPTIMIZER: "optimizer",
          torchbearer.EPOCH: 0,
          torchbearer.MODEL: Mock(),
      }
  
      scheduler = LambdaLR(lr_lambda=0.1, step_on_batch=True)
      scheduler.on_start(state)
  
      lr_mock.assert_called_once_with(
          "optimizer", lr_lambda=0.1, last_epoch=-1
      )
      self.assertTrue(scheduler._step_on_batch)
  
imports: from unittest import TestCase
  from mock import patch, Mock
  import warnings
  import torchbearer
  from torchbearer.bases import _pytorch_version_gt
  from torchbearer.callbacks import TorchScheduler, LambdaLR, StepLR, MultiStepLR, ExponentialLR, CosineAnnealingLR, ReduceLROnPlateau, CyclicLR
label_desc: Use image node_id 1 for calling the TestLambdaLR obj's underlying member method code with example usage: obj.test_lambda_lr(lr_mock) without return types