Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/shelve.pyi

@@ -0,0 +1,34 @@
+import collections
+from typing import Any, Dict, Iterator, Optional, Tuple
+
+class Shelf(collections.MutableMapping[Any, Any]):
+    def __init__(
+        self, dict: Dict[bytes, Any], protocol: Optional[int] = ..., writeback: bool = ..., keyencoding: str = ...
+    ) -> None: ...
+    def __iter__(self) -> Iterator[str]: ...
+    def __len__(self) -> int: ...
+    def __contains__(self, key: Any) -> bool: ...  # key should be str, but it would conflict with superclass's type signature
+    def get(self, key: str, default: Any = ...) -> Any: ...
+    def __getitem__(self, key: str) -> Any: ...
+    def __setitem__(self, key: str, value: Any) -> None: ...
+    def __delitem__(self, key: str) -> None: ...
+    def __enter__(self) -> Shelf: ...
+    def __exit__(self, type: Any, value: Any, traceback: Any) -> None: ...
+    def close(self) -> None: ...
+    def __del__(self) -> None: ...
+    def sync(self) -> None: ...
+
+class BsdDbShelf(Shelf):
+    def __init__(
+        self, dict: Dict[bytes, Any], protocol: Optional[int] = ..., writeback: bool = ..., keyencoding: str = ...
+    ) -> None: ...
+    def set_location(self, key: Any) -> Tuple[str, Any]: ...
+    def next(self) -> Tuple[str, Any]: ...
+    def previous(self) -> Tuple[str, Any]: ...
+    def first(self) -> Tuple[str, Any]: ...
+    def last(self) -> Tuple[str, Any]: ...
+
+class DbfilenameShelf(Shelf):
+    def __init__(self, filename: str, flag: str = ..., protocol: Optional[int] = ..., writeback: bool = ...) -> None: ...
+
+def open(filename: str, flag: str = ..., protocol: Optional[int] = ..., writeback: bool = ...) -> DbfilenameShelf: ...