def setexprOperator2(op):
    """
    Returns a function which performs set to set comparison operations
    """
    if op == 'is':
        return lambda x, y: x == y
    if op == 'is not':
        return lambda x, y: x != y
    if op == 'subset':
        return lambda x, y: x <= y
    if op == 'superset':
        return lambda x, y: x >= y
    if op == 'proper subset':
        return lambda x, y: x < y
    if op == 'proper superset':
        return lambda x, y: x > y
    raise Exception('operator %s not found' % op)
