@mixin lamb-fieldset() {
    .lamb-fieldset-border {
        border: 1px solid nb-theme(color-bg-active);
        -webkit-box-shadow: 0 nb-theme(color-bg-active);
        box-shadow: 5px 5px 0 nb-theme(color-bg-active);
    }
    .lamb-legend-border {
        font-size: nb-theme(header-font-size);
        font-weight: nb-theme(font-weight-bolder);
    }
}