code: function _freezeConfig(config) {
      Object.freeze(config);
  
      for (var key in config) {
          if (typeof config[key] === "object") {
              _freezeConfig(config[key]);
          }
      }
  }
docs: Freezes the configuration object and makes it immutable. This is a deep
  method; all subobjects will also be immutable.
  
  @param {object} config - The current config object