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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def verify_oauth2_token(id_token, request, audience=None):
 """Verifies an ID Token issued by Google's OAuth 2.0 authorization server. Args: id_token (Union[str, bytes]):
 The encoded token. request (google.auth.transport.Request):
 The object used to make HTTP requests. audience (str):
 The audience that this token is intended for. This is typically your application's OAuth 2.0 client ID. If None then the audience is not verified. Returns: Mapping[str, Any]: The decoded token. """

    return verify_token(
        id_token, request, audience=audience,
        certs_url=_GOOGLE_OAUTH2_CERTS_URL)