container-fill.scss

@mixin grid-output($method) {
    // default output methods
    @if $method == float {
        float: left;
        // float styles.
    }
    @if $method == isolation {
        float: left;
        // float styles.
    }
    @container container;
}

// Add mixin extensions here. Might also be useful inside functions.
@fill container {
    @if $method == table-cell {
        // extend foo function with list output.
    }
}

@fill container {
    @if $method == grid-layout {
        // extend foo function with list output.
    }
}