Add SumOp back in

nifty5/operators/operator.py

@@ -152,16 +152,16 @@ class _OpProd(Operator):
         return Linearization(lin1._val*lin2._val, op(x.jac))
 
 
-# class _OpSum(_CombinedOperator):
-#     def __init__(self, ops, _callingfrommake=False):
-#         from ..sugar import domain_union
-#         super(_OpSum, self).__init__(ops, _callingfrommake)
-#         self._domain = domain_union([op.domain for op in self._ops])
-#         self._target = domain_union([op.target for op in self._ops])
-#
-#     def apply(self, x):
-#         res = None
-#         for op in self._ops:
-#             tmp = op(x.extract(op.domain))
-#             res = tmp if res is None else res.unite(tmp)
-#         return res
+class _OpSum(_CombinedOperator):
+    def __init__(self, ops, _callingfrommake=False):
+        from ..sugar import domain_union
+        super(_OpSum, self).__init__(ops, _callingfrommake)
+        self._domain = domain_union([op.domain for op in self._ops])
+        self._target = domain_union([op.target for op in self._ops])
+
+    def apply(self, x):
+        res = None
+        for op in self._ops:
+            tmp = op(x.extract(op.domain))
+            res = tmp if res is None else res.unite(tmp)
+        return res