Extract the content of dvc tree file
    Args:
        self(object) - Repo class instance
        dir_not_exists(bool) - flag for directory existence
        output(object) - OutputLOCAL class instance
    Returns:
        dict - dictionary with keys - paths to file in .dvc/cache
                               values -checksums for that files

def _extract_dir(self, dir_not_exists, output):
    """Extract the content of dvc tree file
    Args:
        self(object) - Repo class instance
        dir_not_exists(bool) - flag for directory existence
        output(object) - OutputLOCAL class instance
    Returns:
        dict - dictionary with keys - paths to file in .dvc/cache
                               values -checksums for that files
    """
    if not dir_not_exists:
        lst = output.dir_cache
        return {i["relpath"]: i["md5"] for i in lst}
    return {}