diff --git a/third_party/2and3/yaml/cyaml.pyi b/third_party/2and3/yaml/cyaml.pyi
index ad2322d2d..0eef81592 100644
--- a/third_party/2and3/yaml/cyaml.pyi
+++ b/third_party/2and3/yaml/cyaml.pyi
@@ -1,8 +1,10 @@
-from typing import Text, Union
+from typing import Any, IO, Mapping, Optional, Sequence, Text, Union
 from typing_extensions import Protocol
 
-from yaml.constructor import BaseConstructor, SafeConstructor
+from yaml.constructor import BaseConstructor, Constructor, SafeConstructor
+from yaml.representer import BaseRepresenter, Representer, SafeRepresenter
 from yaml.resolver import BaseResolver, Resolver
+from yaml.serializer import Serializer
 
 class _Readable(Protocol):
     def read(self, size: int) -> Union[Text, bytes]: ...
@@ -18,3 +20,28 @@ class CLoader(CParser, SafeConstructor, Resolver):
 
 class CSafeLoader(CParser, SafeConstructor, Resolver):
     def __init__(self, stream: Union[str, bytes, _Readable]) -> None: ...
+
+class CDangerLoader(CParser, Constructor, Resolver): ...  # undocumented
+
+class CEmitter(object):
+    def __init__(self, stream: IO[Any], canonical: Optional[Any] = ...,
+                 indent: Optional[int] = ..., width: Optional[int] = ...,
+                 allow_unicode: Optional[Any] = ..., line_break: Optional[str] = ...,
+                 encoding: Optional[Text] = ..., explicit_start: Optional[Any] = ...,
+                 explicit_end: Optional[Any] = ..., version: Optional[Sequence[int]] = ...,
+                 tags: Optional[Mapping[Text, Text]] = ...) -> None: ...
+
+class CBaseDumper(CEmitter, BaseRepresenter, BaseResolver):
+    def __init__(self, stream: IO[Any], default_style: Optional[str] = ...,
+                 default_flow_style: Optional[bool] = ..., canonical: Optional[Any] = ...,
+                 indent: Optional[int] = ..., width: Optional[int] = ...,
+                 allow_unicode: Optional[Any] = ..., line_break: Optional[str] = ...,
+                 encoding: Optional[Text] = ..., explicit_start: Optional[Any] = ...,
+                 explicit_end: Optional[Any] = ..., version: Optional[Sequence[int]] = ...,
+                 tags: Optional[Mapping[Text, Text]] = ...) -> None: ...
+
+class CDumper(CEmitter, SafeRepresenter, Resolver): ...
+
+CSafeDumper = CDumper
+
+class CDangerDumper(CEmitter, Serializer, Representer, Resolver): ...  # undocumented