def parse_cooler_uri(s):
    """
    Parse a Cooler URI string

    e.g. /path/to/mycoolers.cool::/path/to/cooler

    """
    parts = s.split('::')
    if len(parts) == 1:
        file_path, group_path = parts[0], '/'
    elif len(parts) == 2:
        file_path, group_path = parts
        if not group_path.startswith('/'):
            group_path = '/' + group_path
    else:
        raise ValueError('Invalid Cooler URI string')
    return file_path, group_path
