Makes a secure stub for an RPC service.

    Uses / depends on gRPC.

    :type credentials: :class:`google.auth.credentials.Credentials`
    :param credentials: The OAuth2 Credentials to use for creating
                        access tokens.

    :type user_agent: str
    :param user_agent: The user agent to be used with API requests.

    :type stub_class: type
    :param stub_class: A gRPC stub type for a given service.

    :type host: str
    :param host: The host for the service.

    :type extra_options: tuple
    :param extra_options: (Optional) Extra gRPC options passed when creating
                          the channel.

    :rtype: object, instance of ``stub_class``
    :returns: The stub object used to make gRPC requests to a given API.

def make_secure_stub(credentials, user_agent, stub_class, host, extra_options=()):
    """Makes a secure stub for an RPC service.

    Uses / depends on gRPC.

    :type credentials: :class:`google.auth.credentials.Credentials`
    :param credentials: The OAuth2 Credentials to use for creating
                        access tokens.

    :type user_agent: str
    :param user_agent: The user agent to be used with API requests.

    :type stub_class: type
    :param stub_class: A gRPC stub type for a given service.

    :type host: str
    :param host: The host for the service.

    :type extra_options: tuple
    :param extra_options: (Optional) Extra gRPC options passed when creating
                          the channel.

    :rtype: object, instance of ``stub_class``
    :returns: The stub object used to make gRPC requests to a given API.
    """
    channel = make_secure_channel(
        credentials, user_agent, host, extra_options=extra_options
    )
    return stub_class(channel)