def __getitem__(self, cache_key):
        """Retrieve value from a cache key."""
        actual_key = self._convert_cache_key(cache_key)
        try:
            with open(actual_key) as f:
                return json.load(f)
        except (OSError, __HOLE__, IOError):
            raise KeyError(cache_key)
dataset/ETHPy150Open aws/aws-cli/awscli/customizations/assumerole.py/JSONFileCache.__getitem__