code: def test_from_str(self, en, string):
      self.assertEqual(utils.string_to_loss_function(string), en)
  
imports: from unittest import mock
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from tensorflow_privacy.privacy.privacy_tests import utils
label_desc: Use image node_id 1 for calling the LossFunctionFromStringTest obj's underlying member method code with example usage: obj.test_from_str(en, string) without return types