Why it can not parse (div span a{color: #789}) into tree nodes?

[jackiewillen]

For Example.When i have a css like this.
div span a {color: #789};
It need to build a cssom like this body ->div->span->a with four nodes。as below:
{
parentNode: body,
children: {
parentNode: div,
children: {
parentNode: span,
children: {
node: a
}
}
}
}

Why the CSSOM just generate one object property like below?

{ parentStyleSheet: null,
cssRules: [
{
parentRule: null,
parentStyleSheet: "../..",
selectorText: "div span a",
style: {
0: "color",
length: 1,
parentRule: "..",
_importants: { color: "" },
__starts: 7,
color: "#789" }, __starts: , __ends: 20 } ] }

[NV]

That's not how CSSOM works. The current output is correct.