A proxy model does not store data, but presents data from a source model
in another way. It may provide filtering, sorting, or other computed
changes to the source model. A proxy model may be a fully functional
model, that also allows modification of the underlying model.
The example demonstrates the use of a
WSortFilterProxyModel by sorting and/or filtering on a
model containing different cocktails. You can also change the
filtering regular expresssion.