How to get the rendered text content of litehtml::element?

For example:
```html
<h1>
    <a>a     aa</a>
bbb
</h1>
```
I want get the text of h1 displayed on the browser ("a aa bbb"), but litehtml:: element:: get_text() returns the text "\n    a     aa\n    bbb\n".
May I ask if there is such a function? I don't seem to have found it.