(request, audience)
Fetch the ID Token from the current environment.

    This function acquires ID token from the environment in the following order.
    See https://google.aip.dev/auth/4110.

    1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
       to the path of a valid service account JSON file, then ID token is
       acquired using this service account credentials.
    2. If the application is running in Compute Engine, App Engine or Cloud Run,
       then the ID token are obtained from the metadata server.
    3. If metadata server doesn't exist and no valid service account credentials
       are found, :class:`~google.auth.exceptions.DefaultCredentialsError` will
       be raised.

    Example::

        import google.oauth2._id_token_async
        import google.auth.transport.aiohttp_requests

        request = google.auth.transport.aiohttp_requests.Request()
        target_audience = "https://pubsub.googleapis.com"

        id_token = await google.oauth2._id_token_async.fetch_id_token(request, target_audience)

    Args:
        request (google.auth.transport.aiohttp_requests.Request): A callable used to make
            HTTP requests.
        audience (str): The audience that this ID token is intended for.

    Returns:
        str: The ID token.

    Raises:
        ~google.auth.exceptions.DefaultCredentialsError:
            If metadata server doesn't exist and no valid service account
            credentials are found.
Fetch the ID Token from the current environment.
Fetch the ID Token from the current environment .
async def fetch_id_token(request, audience):
    """Fetch the ID Token from the current environment.

    This function acquires ID token from the environment in the following order.
    See https://google.aip.dev/auth/4110.

    1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
       to the path of a valid service account JSON file, then ID token is
       acquired using this service account credentials.
    2. If the application is running in Compute Engine, App Engine or Cloud Run,
       then the ID token are obtained from the metadata server.
    3. If metadata server doesn't exist and no valid service account credentials
       are found, :class:`~google.auth.exceptions.DefaultCredentialsError` will
       be raised.

    Example::

        import google.oauth2._id_token_async
        import google.auth.transport.aiohttp_requests

        request = google.auth.transport.aiohttp_requests.Request()
        target_audience = "https://pubsub.googleapis.com"

        id_token = await google.oauth2._id_token_async.fetch_id_token(request, target_audience)

    Args:
        request (google.auth.transport.aiohttp_requests.Request): A callable used to make
            HTTP requests.
        audience (str): The audience that this ID token is intended for.

    Returns:
        str: The ID token.

    Raises:
        ~google.auth.exceptions.DefaultCredentialsError:
            If metadata server doesn't exist and no valid service account
            credentials are found.
    """
    # 1. Try to get credentials from the GOOGLE_APPLICATION_CREDENTIALS environment
    # variable.
    credentials_filename = os.environ.get(environment_vars.CREDENTIALS)
    if credentials_filename:
        if not (
            os.path.exists(credentials_filename)
            and os.path.isfile(credentials_filename)
        ):
            raise exceptions.DefaultCredentialsError(
                "GOOGLE_APPLICATION_CREDENTIALS path is either not found or invalid."
            )

        try:
            with open(credentials_filename, "r") as f:
                from google.oauth2 import _service_account_async as service_account

                info = json.load(f)
                if info.get("type") == "service_account":
                    credentials = service_account.IDTokenCredentials.from_service_account_info(
                        info, target_audience=audience
                    )
                    await credentials.refresh(request)
                    return credentials.token
        except ValueError as caught_exc:
            new_exc = exceptions.DefaultCredentialsError(
                "GOOGLE_APPLICATION_CREDENTIALS is not valid service account credentials.",
                caught_exc,
            )
            six.raise_from(new_exc, caught_exc)

    # 2. Try to fetch ID token from metada server if it exists. The code works
    # for GAE and Cloud Run metadata server as well.
    try:
        from google.auth import compute_engine
        from google.auth.compute_engine import _metadata

        request_new = requests.Request()
        if _metadata.ping(request_new):
            credentials = compute_engine.IDTokenCredentials(
                request_new, audience, use_metadata_identity_endpoint=True
            )
            credentials.refresh(request_new)
            return credentials.token
    except (ImportError, exceptions.TransportError):
        pass

    raise exceptions.DefaultCredentialsError(
        "Neither metadata server or valid service account credentials are found."
    )
async def fetch_id_token ( request , audience ) : # 1. Try to get credentials from the GOOGLE_APPLICATION_CREDENTIALS environment # variable. credentials_filename = os . environ . get ( environment_vars . CREDENTIALS ) if credentials_filename : if not ( os . path . exists ( credentials_filename ) and os . path . isfile ( credentials_filename ) ) : raise exceptions . DefaultCredentialsError ( "GOOGLE_APPLICATION_CREDENTIALS path is either not found or invalid." ) try : with open ( credentials_filename , "r" ) as f : from google . oauth2 import _service_account_async as service_account info = json . load ( f ) if info . get ( "type" ) == "service_account" : credentials = service_account . IDTokenCredentials . from_service_account_info ( info , target_audience = audience ) await credentials . refresh ( request ) return credentials . token except ValueError as caught_exc : new_exc = exceptions . DefaultCredentialsError ( "GOOGLE_APPLICATION_CREDENTIALS is not valid service account credentials." , caught_exc , ) six . raise_from ( new_exc , caught_exc ) # 2. Try to fetch ID token from metada server if it exists. The code works # for GAE and Cloud Run metadata server as well. try : from google . auth import compute_engine from google . auth . compute_engine import _metadata request_new = requests . Request ( ) if _metadata . ping ( request_new ) : credentials = compute_engine . IDTokenCredentials ( request_new , audience , use_metadata_identity_endpoint = True ) credentials . refresh ( request_new ) return credentials . token except ( ImportError , exceptions . TransportError ) : pass raise exceptions . DefaultCredentialsError ( "Neither metadata server or valid service account credentials are found." )