Как в sass отключить after для последнего элемента?

.how
        display: table-cell
        position: relative
        &:after
            content: url(../img/howsArrow.png)
            position: absolute
            top: 32px
            left: 189px

.how
        display: table-cell
        position: relative
        &:after
            content: url(../img/howsArrow.png)
            position: absolute
            top: 32px
            left: 189px
            &:last-child:after
                    content: ' '