code: public function getSourceContext($name) : Source
      {
          if (!$this->exists($name)) {
              throw new LoaderError(sprintf(
                  'Unable to find template "%s" from template map',
                  $name
              ));
          }
  
          if (!file_exists($this->map[$name])) {
              throw new LoaderError(sprintf(
                  'Unable to open file "%s" from template map',
                  $this->map[$name]
              ));
          }
  
          $content = file_get_contents($this->map[$name]);
          $source = new Source($content, $name, $this->map[$name]);
  
          return $source;
      }
docs: Returns the source context for a given template logical name.
  
  @param string $name The template logical name
  
  @return Source
  
  @throws LoaderError When $name is not found