def _file_to_string(path: str) -> str:
    """
    Reads in a whole file under path, returns it's content.
    File is treated as read-only.
    :param path: the path where to look for the file
    :return: the file's content
    :raises: FileNotFoundError if file does not exist
    """
    with open(path, 'r', encoding="utf-8") as file:
        return file.read()