def METHOD_NAME(source, mountpoint, is_directory):
    return mount_spec_t(
        mount_config = mount_config_t(
            build_source = build_source_t(
                source = source,
                type = "host",
            ),
            default_mountpoint = source if mountpoint == None else mountpoint,
            is_directory = is_directory,
        ),
        mountpoint = None,
        target = None,
    )