small improvements

nifty6/linearization.py

@@ -156,6 +156,7 @@ class Linearization(Operator):
                 return self.new(self._val-other, self._jac, self._metric)
             else:
                 return self.new(self._val+other, self._jac, self._metric)
+        raise RuntimeError("must not get here")
 
     def __add__(self, other):
         return self._myadd(other, False)

nifty6/utilities.py

@@ -27,6 +27,16 @@ __all__ = ["get_slice_list", "safe_cast", "parse_spaces", "infer_space",
            "my_product", "frozendict", "special_add_at", "iscomplextype"]
 
 
+def assertValue(cond, msg):
+    if not cond:
+        raise ValueError(msg)
+
+
+def assertType(cond, msg):
+    if not cond:
+        raise TypeError(msg)
+
+
 def my_sum(iterable):
     return reduce(lambda x, y: x+y, iterable)