'Read things from cache and return id->thing dict.'

@classmethod
def get_things_from_cache(cls, ids, stale=False, allow_local=True):

    cache = cls._cache
    prefix = cls._cache_prefix()
    things_by_id = cache.get_multi(ids, prefix=prefix, stale=stale, allow_local=allow_local, stat_subname=cls.__name__)
    return things_by_id
