def METHOD_NAME(filename):
    """Read the list of folders containing proofs from a json file."""
    if not filename:
        return []
    try:
        with open(filename) as proofs:
            return json.load(proofs)[JSON_KEY]
    except (FileNotFoundError, KeyError):
        raise UserWarning("Can't find key {} in json file {}".format(JSON_KEY, filename))
    except json.decoder.JSONDecodeError:
        raise UserWarning("Can't parse json file {}".format(filename))