@classmethod
def load_cache(cls, calendar_str: str):
    """Load a scheme calendar YAML file with cache.

        >>> %timeit Calendar.load_cache('bacs')
            969 ns ± 10.8 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
        """
    with cls._cache as cache:
        if not calendar_str in cache:
            cache[calendar_str] = cls.load(calendar_str)
        return cache[calendar_str]
