PyYaml: uncomment commented out imports and add missing classmethod decorators (#1439)

* uncomment yaml imports

* yaml: decorate classmethods

third_party/2and3/yaml/__init__.pyi

@@ -1,10 +1,10 @@
 from typing import Any
-# from yaml.error import *
-# from yaml.tokens import *
-# from yaml.events import *
-# from yaml.nodes import *
-# from yaml.loader import *
-# from yaml.dumper import *
+from yaml.error import *  # noqa: F403
+from yaml.tokens import *  # noqa: F403
+from yaml.events import *  # noqa: F403
+from yaml.nodes import *  # noqa: F403
+from yaml.loader import *  # noqa: F403
+from yaml.dumper import *  # noqa: F403
 # TODO: stubs for cyaml?
 # from cyaml import *
 

third_party/2and3/yaml/constructor.pyi

@@ -22,7 +22,9 @@ class BaseConstructor:
     def construct_sequence(self, node, deep=...): ...
     def construct_mapping(self, node, deep=...): ...
     def construct_pairs(self, node, deep=...): ...
+    @classmethod
     def add_constructor(cls, tag, constructor): ...
+    @classmethod
     def add_multi_constructor(cls, tag_prefix, multi_constructor): ...
 
 class SafeConstructor(BaseConstructor):

third_party/2and3/yaml/representer.pyi

@@ -15,7 +15,9 @@ class BaseRepresenter:
     def represent(self, data): ...
     def get_classobj_bases(self, cls): ...
     def represent_data(self, data): ...
+    @classmethod
     def add_representer(cls, data_type, representer): ...
+    @classmethod
     def add_multi_representer(cls, data_type, representer): ...
     def represent_scalar(self, tag, value, style=...): ...
     def represent_sequence(self, tag, sequence, flow_style=...): ...

third_party/2and3/yaml/resolver.pyi

@@ -12,7 +12,9 @@ class BaseResolver:
     resolver_exact_paths = ...  # type: Any
     resolver_prefix_paths = ...  # type: Any
     def __init__(self) -> None: ...
+    @classmethod
     def add_implicit_resolver(cls, tag, regexp, first): ...
+    @classmethod
     def add_path_resolver(cls, tag, path, kind=...): ...
     def descend_resolver(self, current_node, current_index): ...
     def ascend_resolver(self): ...