public function createRFRRequest($hash_in)
 {
     if ($this->num_batch_requests > 0) {
         throw new \RuntimeException("Could not add the RFR Request. A single Litle Request cannot have both an RFR request and batch requests together.");
     }
     if ($this->closed) {
         throw new \RuntimeException("Could not add the RFR Request. This litleRequest is closed.");
     }
     $RFRXml = Obj2xml::rfrRequestToXml($hash_in);
     file_put_contents($this->request_file, Obj2xml::generateRequestHeader($this->config, $this->num_batch_requests), FILE_APPEND);
     file_put_contents($this->request_file, $RFRXml, FILE_APPEND);
     file_put_contents($this->request_file, "</litleRequest>", FILE_APPEND);
     unlink($this->batches_file);
     unset($this->batches_file);
     $this->closed = true;
 }