Some more code quality fixes

jedi/inference/gradual/annotation.py

@@ -220,8 +220,6 @@ def infer_return_types(function, arguments):
             function.get_default_param_context(),
             match.group(1).strip()
         ).execute_annotation()
-        if annotation is None:
-            return NO_VALUES
 
     context = function.get_default_param_context()
     unknown_type_vars = find_unknown_type_vars(context, annotation)

jedi/inference/gradual/stub_value.py

@@ -41,7 +41,7 @@ class StubModuleValue(ModuleValue):
 
     def get_filters(self, origin_scope=None):
         filters = super(StubModuleValue, self).get_filters(origin_scope)
-        next(filters)  # Ignore the first filter and replace it with our own
+        next(filters, None)  # Ignore the first filter and replace it with our own
         stub_filters = self._get_stub_filters(origin_scope=origin_scope)
         for f in stub_filters:
             yield f
@@ -76,7 +76,7 @@ class TypingModuleWrapper(StubModuleValue):
 class TypingModuleContext(ModuleContext):
     def get_filters(self, *args, **kwargs):
         filters = super(TypingModuleContext, self).get_filters(*args, **kwargs)
-        yield TypingModuleFilterWrapper(next(filters))
+        yield TypingModuleFilterWrapper(next(filters, None))
         for f in filters:
             yield f
 

jedi/inference/gradual/typeshed.py

@@ -103,9 +103,6 @@ def import_module_decorator(func):
                 # ``os.path``, because it's a very important one in Python
                 # that is being achieved by messing with ``sys.modules`` in
                 # ``os``.
-                python_parent = next(iter(parent_module_values))
-                if python_parent is None:
-                    python_parent, = inference_state.import_module(('os',), prefer_stubs=False)
                 python_value_set = ValueSet.from_sets(
                     func(inference_state, (n,), None, sys_path,)
                     for n in [u'posixpath', u'ntpath', u'macpath', u'os2emxpath']