Polylang in must-use plugin

Hi,

I would like to affect custom fields to each translated post of one current post.
How can I get the translations id in my must-use plugin ?

Cause this does’nt work at all :

global $idLangs;

$myFrenchId = '1696';
global $polylang;
if(isset($polylang)){
    foreach ($polylang->get_languages_list() as $term){
        $idLangs = pll_get_post($myFrenchId, $term->slug);
    }
}
print_r($idLangs);

Thanks for any answer

https://www.ads-software.com/plugins/polylang/