selector-unify() function returns a selector that matches only elements matched by both $selector1 and $selector2.
|$selector1||Required||Specifies first css selector|
|$selector2||Required||Specifies second css selector|
|selector||Returns a selector that matches only elements matched by both $selector1 and $selector2.|
|null||Returns null if $selector1 and $selector2 don’t match any of the same elements, or if there’s no selector that can express their overlap.|