Literally retrieve CSS pseudo-element (javascript - HTML)

See more:

Javascript

CSS

HTML

element

From this code:

<label for="...">
    ::before
    < span class="label-text"> ... < /span > </label>
    ::after

how could ::after be extracted ?

(Note: Spaces have been inserted inside the span tags, in order to be displayed by this editor.)

It corresponds to the checked state of a checkbox
(that's masked with CSS).
When the checkbox is unchecked, ::after disappears.

I would like to check whether ::after is present or not.

What I have tried:

Currently trying to check this using Robot Framework, whether ::after is present or not.

However, I would need the simplest solution possible for this check.
I'm thinking more of a simple JavaScript that can solve this.