code: def test_backend_selection(self):
      backend = fiber.backend.auto_select_backend()
      assert backend == fiber.config.default_backend
  
      try:
          orig_val = os.environ.get("KUBERNETES_SERVICE_HOST", "")
          os.environ["KUBERNETES_SERVICE_HOST"] = "127.0.0.1"
  
          backend = fiber.backend.auto_select_backend()
          assert backend == "kubernetes"
      finally:
          os.environ["KUBERNETES_SERVICE_HOST"] = orig_val
  
file_path: fiber/tests/test_backend.py
imports: import os
  import fiber.backend
  import fiber.config
  import fiber.docker_backend
  import fiber.kubernetes_backend
  import fiber.local_backend
label_desc: Use image node_id 1 for calling the TestBackend obj's underlying member method code with example usage: obj.test_backend_selection() without return types