def SET_IS_SUBSET(*expressions):
    """
    Takes two arrays and returns true when the first array is a subset of the second,
    including when the first array equals the second array, and false otherwise.
    https://docs.mongodb.com/manual/reference/operator/aggregation/setIsSubset/
    for more details
    :param expressions: The arrays (expressions)
    :return: Aggregation operator
    """
    return {'$setIsSubset': list(expressions)}
