/**
  * Get the previous used sibbling of an element.
  *
  * @param Tracker_FormElement $element
  *
  * @return Tracker_FormElement null if not found
  */
 public function getPreviousSibling($element)
 {
     $tracker_id = $element->getTrackerId();
     $element_id = $element->getId();
     if ($row = $this->getDao()->searchPreviousUsedSibling($tracker_id, $element_id)->getRow()) {
         return $this->getCachedInstanceFromRow($row);
     }
 }