code: function getTemplateContentFromFile(filename, options, callback) {
    var isAsync = callback && typeof callback === 'function';
  
    // sync
    if (!isAsync) {
      return fs.readFileSync(filename, 'utf8');
    }
  
    // async
    fs.readFile(filename, 'utf8', function(err, str) {
      if (err) {
        callback(new Error('Failed to open view file (' + filename + ')'));
        return;
      }
  
      try {
        callback(null, str);
      }
      catch (err) {
        callback(err);
      }
    });
  }
docs: Gets the template content from a file
  If callback is passed, it will be called asynchronously.
  @param {String} filename The path to the template
  @param {Object} options The options sent by express
  @param {Function} callback (Optional) The async node style callback