Add typing for context managers returning Self

`Self` was introduced in python 3.11. Use `Self` from typing_extensions for previous Python versions

wx/lib/busy.py

@@ -13,9 +13,15 @@ A class like :class:`wx.BusyInfo` but which doesn't take up so much space by def
 and which has a nicer look.
 """
 
+import sys
 import wx
 from wx.lib.stattext import GenStaticText as StaticText
 
+if sys.version_info >= (3, 11):
+    from typing import Self
+else:
+    from typing_extensions import Self
+
 #---------------------------------------------------------------------------
 
 
@@ -68,7 +74,7 @@ class BusyInfo(object):
 
 
     # Magic methods for using this class as a Context Manager
-    def __enter__(self):
+    def __enter__(self) -> Self:
         return self
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.Close()

wx/lib/plot/utils.py

@@ -13,6 +13,7 @@ This is a collection of utilities used by the :mod:`wx.lib.plot` package.
 __docformat__ = "restructuredtext en"
 
 # Standard Library
+import sys
 import functools
 import inspect
 import itertools
@@ -22,6 +23,12 @@ from warnings import warn as _warn
 import wx
 import numpy as np
 
+if sys.version_info >= (3, 11):
+    from typing import Self
+else:
+    from typing_extensions import Self
+
+
 class PlotPendingDeprecation(wx.wxPyDeprecationWarning):
     pass
 
@@ -195,7 +202,7 @@ class TempStyle(object):
 
         return wrapper
 
-    def __enter__(self):
+    def __enter__(self) -> Self:
         self._save_items(self.dc)
         return self