$columns: ( 'article': 9, 'aside': 3, 'full-width': 12, 'none': 0 );

// index.php
div[role="index"] {
    // row
    main {
        @include grid-row();
        // column
        article {
            @include grid-column(columns('article'));
        }
        // sidebar
        aside {
            @include grid-column(columns('aside'));
        }
    }
}

@include grid-column(#{map-get($columns, 'article')});
@include grid-column(#{map-get($columns, 'aside')});