Add a test for docstring in call signature

jedi/evaluate_representation.py

@@ -169,7 +169,7 @@ class Instance(use_metaclass(cache.CachedMetaClass, Executable)):
 
     def __getattr__(self, name):
         if name not in ['start_pos', 'end_pos', 'name', 'get_imports',
-                                                        'docstr', 'asserts']:
+                'doc', 'docstr', 'asserts']:
             raise AttributeError("Instance %s: Don't touch this (%s)!"
                                     % (self, name))
         return getattr(self.base, name)