code: public function parse(Twig_TokenStream $stream)
      {
          if (null === $this->parser) {
              $this->parser = new Twig_Parser($this);
          }
  
          return $this->parser->parse($stream);
      }
docs: Converts a token stream to a node tree.
  
  @return Twig_Node_Module
  
  @throws Twig_Error_Syntax When the token stream is syntactically or semantically wrong