about FAQ 2. css will be ignored when defined with parent selector.
like
<div id="parent"><div class="child"></div></div>
#parent .child{
background: red;
}
if we choose the child element as $0 , the result is empty.
firstly, checking whether the last selector is matched. matched in this case .child
$0.matched('.child') // true
const parentSelector = '#parent';
const parentElement = document.querySelector(parentSelector);
const isMatched = parentElement.contain($0);
<div id="the-root-for-wrapper-result"><div class="child"></div></div>
#the-root-for-wrapper-result .child{
background: red;
}