code: protected function parseRelationship($node)
      {
          $rel = array();
  
          $x = preg_replace('/\(.*?\)/', '', $node->text('marc:subfield[@code="w"]'));
          if (!empty($x)) {
              $rel['id'] = $x;
          }
  
          $x = $node->text('marc:subfield[@code="t"]');
          if (!empty($x)) {
              $rel['title'] = $x;
          }
  
          $x = $node->text('marc:subfield[@code="g"]');
          if (!empty($x)) {
              $rel['parts'] = $x;
          }
  
          $x = $node->text('marc:subfield[@code="x"]');
          if (!empty($x)) {
              $rel['issn'] = $x;
          }
  
          $x = $node->text('marc:subfield[@code="z"]');
          if (!empty($x)) {
              $rel['isbn'] = $x;
          }
  
          return $rel;
      }
docs: Parse a "relationship node", one that have links to other records encapsulated.
  
  @param QuiteSimpleXmlElement $node
  
  @return array