code: public function add($name, $path)
      {
          if ($this->exists($name)) {
              throw new Twig_Error_Loader(sprintf(
                  'Name "%s" already exists in map',
                  $name
              ));
          }
          $this->map[$name] = $path;
          return $this;
      }
docs: Add to the map.
  
  @param string $name
  @param string $path
  @throws \Twig_Error_Loader
  @return MapLoader