code: func hasDescendantSelector(a Selector) Selector {
  	return func(n *html.Node) bool {
  		if n.Type != html.ElementNode {
  			return false
  		}
  		return hasDescendantMatch(n, a)
  	}
  }
docs: // hasDescendantSelector returns a selector that matches elements
  // with any descendant that matches a.