code: def test_str_enum(self):
      output = look_up_option("C", {"A", "B"}, default=None)
      self.assertEqual(output, None)
      self.assertEqual(list(_CaseStrEnum), ["A", "B"])
      self.assertEqual(_CaseStrEnum.MODE_A, "A")
      self.assertEqual(str(_CaseStrEnum.MODE_A), "A")
      self.assertEqual(look_up_option("A", _CaseStrEnum), "A")
  
file_path: MONAI/tests/test_look_up_option.py
imports: from __future__ import annotations
  import unittest
  from enum import Enum
  from parameterized import parameterized
  from monai.utils import StrEnum, look_up_option
label_desc: Use image node_id 3 for calling the TestLookUpOption obj's underlying member method code with example usage: obj.test_str_enum() without return types