public function rel($urn)
    {
        $match = $this->rels([$urn]);
        return count($match) > 0 ? $match[0] : null;
    }
public function rel($urn)
    {
        $match = $this->rels([$urn]);
        return count($match) > 0 ? $match[0] : null;
    }
public function rel ( $ urn ) { $ match = $ this -> rels ( [ $ urn ] ) ; return count ( $ match ) > 0 ? $ match [ 0 ] : null ; }
Get the first link matching a URN

@param string $urn the name to match on
@return CollectionDocJsonLink the matched link
Get the first link matching a URN