def METHOD_NAME(self) -> Iterator[str]:
    """Return build args used as the image ref in `FROM` instructions.
    Example:
        ARG BASE_IMAGE
        FROM ${BASE_IMAGE}
    """
    for cmd in self.get_all("FROM"):
        build_arg = self._get_image_ref_build_arg(cmd.value[0])
        if build_arg:
            yield build_arg