Add _Pickler and _Unpickler to stdlib/pickle (#5506)

dreiss · web-flow · commit 1547035a95d1 · 2021-05-19T20:57:07.000+03:00
These are the pure-Python pickle implementation, and are sometimes used
by code that wants to extend or override parts of the
pickling/unpickling process.
diff --git a/stdlib/pickle.pyi b/stdlib/pickle.pyi
@@ -169,3 +169,6 @@ FRAME: bytes
 
 def encode_long(x: int) -> bytes: ...  # undocumented
 def decode_long(data: bytes) -> int: ...  # undocumented
+
+_Pickler = Pickler  # undocumented
+_Unpickler = Unpickler  # undocumented
