@function _shape-size-stripper($shape-size) {
    $shape-size-spec: null;
    @each $value in $shape-size {
        @if ($value == "cover") or ($value == "contain") {
            $value: null;
        }
        $shape-size-spec: "#{$shape-size-spec} #{$value}";
    }
    @return $shape-size-spec;
}