removed all the weakref stuff again. It didn't speed up anything, but made things much more complicated

jedi/keywords.py

@@ -36,11 +36,10 @@ class Keyword(object):
     def __init__(self, name, pos):
         self.name = name
         self.start_pos = pos
+        self.parent = builtin.Builtin.scope
 
-    def parent(self):
-        return builtin.Builtin.scope
-
-    get_parent_until = parent
+    def get_parent_until(self):
+        return self.parent
 
     @property
     def names(self):