code: function render(filename, options, callback) {
    var isAsync = callback && typeof callback === 'function';
  
    if (!isAsync) {
      return renderSync(filename, options)
    }
  
    getTemplate(filename, options, function(err, template) {
      if (err) {
        return callback(err);
      }
  
      template.render({ model: options, }, callback);
    });
  }
docs: Render a template
  @param {String} filename The path to the file
  @param {Object} options The model to pass to the view
  @param {Function} callback (Optional) The async node style callback