private function processKeyIsValidFunction($key)
 {
     $eZSIBlock = new eZSIBlockFunction();
     $ttl = '1s';
     $functionParameters = $this->buildFunctionParameters($key, $ttl);
     return $eZSIBlock->keyIsValid($this->templateResource, $this->textElements, $this->functionChildren, $functionParameters, $this->functionPlacement, $this->rootNamespace, $this->currentNamespace);
 }