Move this function out to be VTK-specific, probably into vtkModuleTesting.cmake. Each module would then need to manually call this function. It currently assumes it is in VTK itself.
Support freezing the Python package. This should create a header and the associated target should provide an interface for including this header. The target should then be exported and the header installed properly.
This is the workaround to deal with GPUVolumeRayCastMapper not able to handle extents starting from non zero values. There is not a easy fix in the GPU volume ray cast mapper hence this fix has been introduced.