def ADD(*expressions):
    """
    Adds numbers together or adds numbers and a date.
    If one of the arguments is a date, $add treats the other arguments as milliseconds to add to the date.
    See https://docs.mongodb.com/manual/reference/operator/aggregation/add/
    for more details
    :param expressions: The numbers or fields of number
    :return: Aggregation operator
    """
    return {'$add': list(expressions)}