Change Details

The `role` hash key is hashed twice: * first, when calling `contains` method; * second, when using `operator[]`. We can do better by using iterators.

The `role` hash key is hashed twice: * first, when calling `contains` method; * second, when using `operator[]`. We can do better by using [QHash::value](http://doc.qt.io/qt-5/qhash.html#value).

The `role` hash key is hashed twice: * first, when calling `contains` method; * second, when using `operator[]`. We can do better by using iterators[QHash::value](http://doc.qt.io/qt-5/qhash.html#value).