/**
  * Renders the ext_key column.
  *
  * @param DevlogEntryModel $entry
  *
  * @return string
  */
 protected function formatExtKeyColumn(DevlogEntryModel $entry)
 {
     return sprintf('<button ' . 'type="submit" ' . 'class="button button-extkey severity-%1$s" ' . 'name="SET[mklogDevlogEntryExtKey]" ' . 'value="%1$s" ' . 'title="Filter %1$s"' . '>%1$s</button>', $entry->getExtKey());
 }