code: func descendantSelector(a, d Selector) Selector {
  	return func(n *html.Node) bool {
  		if !d(n) {
  			return false
  		}
  
  		for p := n.Parent; p != nil; p = p.Parent {
  			if a(p) {
  				return true
  			}
  		}
  
  		return false
  	}
  }
docs: // descendantSelector returns a Selector that matches an element if
  // it matches d and has an ancestor that matches a.