code: private function getTemplate($format)
      {
          $filepath = sprintf('%s/%s.svg', $this->templatesDirectory, $format);
  
          if (!file_exists($filepath)) {
              throw new \InvalidArgumentException(sprintf('No template for format %s', $format));
          }
  
          return file_get_contents($filepath);
      }
docs: @param $format
  
  @return string SVG content of the template