Is currently done in `ImageStatisticsCalculationJob` (but that's not the job of the class).
Why `m_StatisticContainers`? One instance of ImageStatisticsCalculator should only have one container. The container includes the timegeometry (and in case of 4D the respective 3D geometries)
In `template < typename TPixel, unsigned int VImageDimension > void ImageStatisticsCalculator::InternalCalculateStatisticsUnmasked(typename itk::Image< TPixel, VImageDimension >* image, TimeGeometry* timeGeometry, TimeStepType timeStep)`:
```
if(m_StatisticContainers.empty() || m_StatisticContainers.back()->TimeStepExists(timeStep)) {
...
}
```
This is an umplausible/inconsequent implementation. It assumes that the container has the complete `TimeGeometry` (which is not the case, see T25561), but the `ImageStatisticsContainer` currently only has one timestep.