docs: def measureSize(self, diffTo, diffFrom, estimatedSize, chunkSize, isInteractive):
          """ Spend some time to get an accurate size. """
          diff = self.toObj.diff(diffTo, diffFrom, estimatedSize)
          isInteractive = self.toObj.bool(isInteractive)
          self.butterStore.showProgress = None if isInteractive else False
          self.butterStore.measureSize(diff, int(chunkSize))
          return self.toDict.diff(diff)