add_filter(
   'friends_parser_confidence',
    function(
        $confidence,
        $slug,
        string $link_url,
        $feed
    ) {
        // Your code here.
        return $confidence;
    },
    10,
    4
);

apply_filters( 'friends_parser_confidence', $confidence, $slug, $link_url, $feed )

apply_filters( 'friends_parser_confidence', $confidence, $slug, $url, $feed )