code: def test_lambda_fn(self):
      obj = {"activation": lambda x: x**2}
      with self.assertRaisesRegex(
          ValueError, "arbitrary code execution"
      ):
          self.roundtrip(obj, safe_mode=True)
  
      _, new_obj, _ = self.roundtrip(obj, safe_mode=False)
      self.assertEqual(obj["activation"](3), new_obj["activation"](3))
  
imports: import json
  import numpy
  import pytest
  import keras
  from keras import ops
  from keras import testing
  from keras.saving import serialization_lib
label_desc: Use image node_id 7 for calling the SerializationLibTest obj's underlying member method code with example usage: obj.test_lambda_fn() without return types