fixes

nifty5/energies/kl.py

 from builtins import *
 from ..minimization.energy import Energy
-from ..utilities import memo
+from ..utilities import memo, my_sum
 
 
 class SampledKullbachLeiblerDivergence(Energy):

nifty5/minimization/energy.py

@@ -130,6 +130,7 @@ class Energy(NiftyMetaBase()):
         return None
 
     def makeInvertible(self, controller, preconditioner=None):
+        from .iteration_controller import IterationController
         if not isinstance(controller, IterationController):
             raise TypeError
         return CurvatureInversionEnabler(self, controller, preconditioner)