static private function properties (array $props)
  {
    return "<h6>Assigned properties</h6><table class=grid>
" . str_replace (["'", '...'], ["<i>'</i>", '<i>...</i>'], implode ('',
        map ($props, function ($v, $k) {
          return "<tr><th>$k<td>" .
                 (is_string ($v) ? "'" . htmlspecialchars (trimText ($v, 300, '...')) . "'" : Debug::toString ($v));
        })), $o) . "
</table>";
  }