add FIXME

nifty5/minimization/energy_sum.py

@@ -37,6 +37,8 @@ class EnergySum(Energy):
         eout = []
         fout = []
         EnergySum._unpackEnergies(energies, factors, 1., eout, fout)
+        # FIXME we need to reach an agreement about how we want to deal
+        # with domain and field compatibility. Until then, we relax te check.
         # for e in eout[1:]:
         #     if not e.position.isEquivalentTo(eout[0].position):
         #         raise ValueError("position mismatch")