add pre_commit.yaml module

pre_commit/yaml.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+
+import functools
+from typing import Any
+
+import yaml
+
+Loader = getattr(yaml, 'CSafeLoader', yaml.SafeLoader)
+yaml_load = functools.partial(yaml.load, Loader=Loader)
+Dumper = getattr(yaml, 'CSafeDumper', yaml.SafeDumper)
+
+
+def yaml_dump(o: Any, **kwargs: Any) -> str:
+    # when python/mypy#1484 is solved, this can be `functools.partial`
+    return yaml.dump(
+        o, Dumper=Dumper, default_flow_style=False, indent=4, sort_keys=False,
+        **kwargs,
+    )