str]): The optional OAuth 2.0 token exchange audience field.
            scopes (Optional[Sequence[str]]): The optional list of scopes to use.
            requested_token_type (Optional[str]): The optional OAuth 2.0 token exchange requested
                token type.
            actor_token (Optional[str]): The optional OAuth 2.0 token exchange actor token.
            actor_token_type (Optional[str]): The optional OAuth 2.0 token exchange actor token type.
            additional_options (Optional[Mapping[str, str]]): The optional additional
                non-standard Google specific options.
            additional_headers (Optional[Mapping[str, str]]): The optional additional
                headers to pass to the token exchange endpoint.

        Returns:
            Mapping[str, str]: The token exchange JSON-decoded response data containing
                the requested token and its expiration time.

        Raises:
            google.auth.exceptions.OAuthError: If the token endpoint returned
                an error.
        ú