def load_file(filename: str) -> list:
    """Read file containing survey responses

    :param filename: Location of survey response file
    :return: List of survey responses by group
    """
    groups = []
    gp = []
    with open(filename, 'r') as f:
        for line in f:
            if line == '\n':
                groups.append(gp)
                gp = []
            else:
                gp.append(frozenset(line[:-1]))
    groups.append(gp)
    return groups