public static function get()
 {
     if (is_null(tfResources::$instance)) {
         tfResources::$instance = new tfResources();
     }
     return tfResources::$instance;
 }
 /**
  * Sets the output.
  * @param standardOutput $output The project output.
  */
 public function setOutput($output)
 {
     $res = tfResources::get();
     if (!in_array($output, $res->outputs)) {
         throw new SystemException('The used output "' . $output . '" is not supported by TypeFriendly.');
     }
     $this->output = $output;
 }