Custom WP_List_Table: How to create an unapproved row?

In this Example, let’s assume every item had the attribute $item['approved'] with values Zero unapproved and One for approved.

How can I get the rows of the “unapproved books” to be yellow?

(well, it’s not about the yellow, but about the WP standard compliant procedure of marking rows as unapproved)

Well, the yellow comes from

<tr class="unapproved">

and this is, in crass contrast to what the usual WP_List_Table introduction might suggest, not an automatism, but generated very verbatim:

See e.g. single_row() in wp-admin/includes/class-wp-comments-list-table.php:

function single_row( $a_comment ) {
                global $post, $comment;

                $comment = $a_comment;
                $the_comment_class = join( ' ', get_comment_class( wp_get_comment_status( $comment->comment_ID ) ) );

                $post = get_post( $comment->comment_post_ID );

                $this->user_can = current_user_can( 'edit_comment', $comment->comment_ID );

                echo "<tr id='comment-$comment->comment_ID' class="$the_comment_class">";
                echo $this->single_row_columns( $comment );
                echo "</tr>\n";
        }

which overrides the standard method inherited from wp-admin/includes/class-wp-list-table.php