code: public function initRuntime()
      {
          $this->runtimeInitialized = true;
  
          foreach ($this->getExtensions() as $name => $extension) {
              if (!$extension instanceof Twig_Extension_InitRuntimeInterface) {
                  $m = new ReflectionMethod($extension, 'initRuntime');
  
                  if ('Twig_Extension' !== $m->getDeclaringClass()->getName()) {
                      @trigger_error(sprintf('Defining the initRuntime() method in the "%s" extension is deprecated since version 1.23. Use the `needs_environment` option to get the Twig_Environment instance in filters, functions, or tests; or explicitly implement Twig_Extension_InitRuntimeInterface if needed (not recommended).', $name), E_USER_DEPRECATED);
                  }
              }
  
              $extension->initRuntime($this);
          }
      }
docs: Initializes the runtime environment.
  
  @deprecated since 1.23 (to be removed in 2.0)