selection_properties.go
func (s *Selection) CSS(property string) (string, error) {
	return s.hasProperty(element.Element.GetCSS, property, "CSS property")
}
func (s *Selection) CSS(property string) (string, error) {
	return s.hasProperty(element.Element.GetCSS, property, "CSS property")
}
// CSS returns a CSS style property value for exactly one element.