private function getURIKeys()
 {
     if (is_null($this->URIKeys)) {
         $parser = new YAMLKeyParser($this->logger);
         $this->URIKeys = $parser->getKeys();
         unset($parser);
     }
     return $this->URIKeys;
 }
 private function swapURITags($tag)
 {
     if (is_null($this->URIKeys)) {
         $parser = new YAMLKeyParser($this->logger);
         $this->URIKeys = $parser->getKeys();
         unset($parser);
     }
     if (!array_key_exists($ag, $this->URIKeys)) {
         throw new URINotFoundException('HTMLTagHander::' . $tag . ' not found in URIKeys');
     }
     return '/' . $this->URIKeys[$tag];
 }