Fix some more context issues

jedi/inference/base_value.py

@@ -120,6 +120,10 @@ class HelperValueMixin(object):
             return class2.is_same_class(self)
         return self == class2
 
+    @memoize_method
+    def as_context(self):
+        return self._as_context()
+
 
 class Value(HelperValueMixin, BaseValue):
     """
@@ -222,10 +226,6 @@ class Value(HelperValueMixin, BaseValue):
         # The root value knows if it's a stub or not.
         return self.parent_context.is_stub()
 
-    @memoize_method
-    def as_context(self):
-        return self._as_context()
-
     def _as_context(self):
         raise NotImplementedError('Not all values need to be converted to contexts')