code: def test_from_default_env(mocker):
      """Test that we can construct default reading region from env var."""
      # Patch gcloud output
      mocker.patch(
          "wandb.sdk.launch.environment.gcp_environment.subprocess.check_output",
          return_value=b"unset",
      )
      # Patch env vars
      mocker.patch.dict(
          os.environ,
          {
              GCP_REGION_ENV_VAR: "us-central1",
          },
      )
      environment = GcpEnvironment.from_default()
      assert environment.region == "us-central1"
  
file_path: wandb/tests/pytest_tests/unit_tests/test_launch/test_environment/test_gcp.py
imports: import os
  from unittest.mock import MagicMock
  import pytest
  from google.api_core.exceptions import Forbidden, GoogleAPICallError, NotFound
  from google.auth.exceptions import DefaultCredentialsError, RefreshError
  from wandb.sdk.launch.environment.gcp_environment import GCP_REGION_ENV_VAR, GcpEnvironment, get_gcloud_config_value
  from wandb.sdk.launch.errors import LaunchError
label_desc: Use image node_id 3 for calling a global function with example usage: test_from_default_env(mocker) without return types