def mark_seen(self):
        """
        Mark the selected message or comment as seen.
        """
        data = self.get_selected_item()
        if data['is_new']:
            with self.term.loader('Marking as read'):
                data['object'].mark_as_read()
            if not self.term.loader.exception:
                data['is_new'] = False
        else:
            with self.term.loader('Marking as unread'):
                data['object'].mark_as_unread()
            if not self.term.loader.exception:
                data['is_new'] = True

        Mark the selected message or comment as seen.
        
rtv/inbox_page.py