filesystem, it is treated as an
            empty file. If `custom_ops_yaml_path` exists, the contents of that
            file are appended to the yaml input to be parsed.
        custom_ops_yaml_path: Path to a custom_ops.yaml file to parse. If
            the path does not exist in the filesystem, it is ignored.
        selector: For selective build.
        use_aten_lib: We use this flag to determine if we want to generate native
            functions. In ATen mode we should generate out= variants.
    Returns:
        A tuple with two elements:
        [0]: The parsed results of concatenating the contents of
             `native_yaml_path` and `custom_ops_yaml_path`.
        [1]: The parsed results of the contents of `custom_ops_yaml_path`, if
             present. If not present, None.
    r