Use even more stubs to get more complex completions for e.g. strings working

jedi/evaluate/base_context.py

@@ -19,6 +19,8 @@ from jedi.evaluate.utils import safe_property
 from jedi.evaluate.cache import evaluator_as_method_param_cache
 from jedi.cache import memoize_method
 
+_sentinel = object()
+
 
 class HelperContextMixin(object):
     def get_root_context(self):
@@ -185,6 +187,11 @@ class Context(HelperContextMixin, BaseContext):
             return clean_scope_docstring(self.tree_node)
         return None
 
+    def get_safe_value(self, default=_sentinel):
+        if default is _sentinel:
+            raise ValueError("There exists no safe value for context %s" % self)
+        return default
+
     def py__call__(self, arguments):
         debug.warning("no execution possible %s", self)
         return NO_CONTEXTS