add_filter(
   'friends_react',
    function(
        $ret,
        $post_id,
        string $2b50,
        $taxonomy_username = null
    ) {
        // Your code here.
        return $ret;
    },
    10,
    3
);

apply_filters( 'friends_react', null, $post_id, '2b50', $taxonomy_username )

apply_filters( 'friends_react', null, $post_id, $reaction )

apply_filters( 'friends_react', null, $post_id, $reaction )