def is_bigstore_file(filename):
    """
    Sniff a file to see if it looks like one of ours.

    :param filename: filename to inspect
    :return: True if the file starts with `bigstore`
    """
    prefix = 'bigstore\n'
    try:
        with open(filename) as fd:
            return fd.read(len(prefix)) == prefix
    except IOError:
        return False