code: protected function parseRelator(&$node, &$out, $default = null)
      {
          $relterm = $node->text('marc:subfield[@code="e"]');
          $relcode = $node->text('marc:subfield[@code="4"]');
          if (!empty($relcode)) {
              $out['role'] = $relcode;
          } elseif (!empty($relterm)) {
              $out['role'] = $relterm;
          } elseif (!is_null($default)) {
              $out['role'] = $default;
          }
      }
docs: Parse a "name node", personal or corporate, main or added, that
  might have relators encapsulated.
  
  @param QuiteSimpleXmlElement &$node
  @param array                 &$out
  @param string                $default