code: def test_lambda_metric_batch(self):
      metric = "test"
      metric = lambda_metric("test")(metric)
      self.assertTrue(isinstance(metric, BatchLambda))
      self.assertTrue(metric._metric_function == "test")
  
imports: import unittest
  from mock import Mock
  import torchbearer.metrics
  from torchbearer.metrics import default_for_key, lambda_metric, EpochLambda, BatchLambda
label_desc: Use image node_id 5 for calling the TestDecorators obj's underlying member method code with example usage: obj.test_lambda_metric_batch() without return types