Document the fact that StorageDevice.format is always a DeviceFormat.
Document the fact that StorageDevice.format is always a DeviceFormat.

StorageDevice.format should never be anything other than an instance
of DeviceFormat or one of its subclasses. All block devices contain data
that is arranged according to some format. The case of empty or
uninitialized or unrecognized formatting is represented by the base class
DeviceFormat.

AdamWill/blivet,vojtechtrefny/blivet,vpodzime/blivet,rvykydal/blivet,rhinstaller/blivet,vojtechtrefny/blivet,vpodzime/blivet,AdamWill/blivet,jkonecny12/blivet,rvykydal/blivet,jkonecny12/blivet,rhinstaller/blivet