/**
  * Fetch the data from the specified location of the Xref.
  *
  * @param Xref $xref
  * @param boolean $force If true and Xref already fetched, force the resolver to fetch the data again.
  * @throws \Exception
  */
 public static function resolve(Xref $xref, $force = false)
 {
     $xref->setResolved(true);
 }