Custom avatar image based on image field in WP-Members

add_filter( 'get_avatar', 'wpmem_ul_my_custom_avatar', 10, 6 );
function wpmem_ul_my_custom_avatar( $avatar, $id_or_email, $size, $default, $alt, $args ) {
    
    // What is the custom image field's meta key?
    // Set this value to match the meta key of your custom image field.
    $meta_key = "image_test";
    
    // Nothing really to change below here, unless
    // you want to change the <img> tag HTML.
    $user = false;
    if ( is_numeric( $id_or_email ) ) {
        $user = get_user_by( 'id' , (int)$id_or_email );
    } elseif ( is_object( $id_or_email ) ) {
        if ( ! empty( $id_or_email->user_id ) ) {
            $id = (int)$id_or_email->user_id;
            $user = get_user_by( 'id' , $id );
        }
    } else {
        $user = get_user_by( 'email', $id_or_email );    
    }
    if ( $user && is_object( $user ) ) {
        $post_id = get_user_meta( $user->ID, $meta_key, true );
        if ( $post_id ) {
            $attachment_url = wp_get_attachment_url( $post_id );
        
            // HTML for the avatar <img> tag.  This is WP default.
            // $avatar = '<img alt="' . $alt . '" src="' . $attachment_url . '" class="avatar avatar-' . $size . ' photo" height="' . $size . '" width="' . $size . '" />';
            $avatar = sprintf(
                "<img alt='%s' src='%s' class='%s' height='%d' width='%d' %s/>",
                esc_attr( $alt ),
                esc_url( $attachment_url ),
                esc_attr( "avatar avatar-" . $size . " photo" ),                
                (int) $args['height'],
                (int) $args['width'],
                $args['extra_attr']
            );
        }
    }
    return $avatar;
}