code: def test_config_env(self):
      import os
  
      old_val = os.environ.get("FIBER_IMAGE", None)
      os.environ["FIBER_IMAGE"] = "image-from-env:latest"
      try:
          fiber.init()
          assert fiber_config.image == "image-from-env:latest"
      finally:
          if old_val is None:
              del os.environ["FIBER_IMAGE"]
          else:
              os.environ["FIBER_IMAGE"] = old_val
          fiber.init()
  
file_path: fiber/tests/test_config.py
imports: import fiber
  import fiber.config
  import logging
  import pytest
  import time
  import fiber.config
label_desc: Use image node_id 3 for calling the TestMisc obj's underlying member method code with example usage: obj.test_config_env() without return types