code: function getAccessorFn(bs, propName) {
              return function () {
                  if (arguments.length == 0) {
                      return bs[propName];
                  } else {
                      bs[propName] = arguments[0];
                  }
              };
          }
docs: A caching version of this 'getAccessorFn' was removed as the perf gain is minimal or negative based on simple testing.