openpyxl: Use duck typing for workbook sheets (#11718)

stubs/openpyxl/openpyxl/workbook/workbook.pyi

@@ -1,7 +1,7 @@
 from _typeshed import Incomplete, Unused
 from collections.abc import Iterator
 from datetime import datetime
-from typing import Any, Final
+from typing import Any, Final, type_check_only
 from typing_extensions import TypeAlias, deprecated
 from zipfile import ZipFile
 
@@ -17,6 +17,23 @@ from openpyxl.worksheet.worksheet import Worksheet
 _WorkbookWorksheet: TypeAlias = Worksheet | WriteOnlyWorksheet | ReadOnlyWorksheet
 _WorkbookSheet: TypeAlias = _WorkbookWorksheet | Chartsheet
 
+# The type of worksheets in a workbook are the same as the aliases above.
+# However, because Worksheet adds a lots of attributes that other _WorkbookChild subclasses
+# don't have (ReadOnlyWorksheet doesn't even inherit from it), this ends up being too
+# disruptive to the typical usage of openpyxl where sheets are just Worksheets.
+# Using Any may just lose too much type information and duck-typing
+# from Worksheet works great here. Allowing instance type check, even if direct
+# type comparison might be wrong.
+@type_check_only
+class _WorksheetLike(  # type: ignore[misc] # Incompatible definitions, favor Worksheet
+    Worksheet, WriteOnlyWorksheet, ReadOnlyWorksheet
+): ...
+
+@type_check_only
+class _WorksheetOrChartsheetLike(  # type: ignore[misc] # Incompatible definitions, favor Worksheet
+    Chartsheet, _WorksheetLike
+): ...
+
 INTEGER_TYPES: Final[tuple[type[int]]]
 
 class Workbook:
@@ -37,7 +54,7 @@ class Workbook:
     views: Incomplete
     # Useful as a reference of what "sheets" can be for other types
     # ExcelReader can add ReadOnlyWorksheet in read_only mode.
-    # _sheets: list[_WorkbookSheet]
+    # _sheets: list[_WorksheetOrChartsheetLike]
     def __init__(self, write_only: bool = False, iso_dates: bool = False) -> None: ...
     @property
     def epoch(self) -> datetime: ...
@@ -52,7 +69,7 @@ class Workbook:
     @property
     def excel_base_date(self) -> datetime: ...
     @property
-    def active(self) -> _WorkbookSheet | None: ...
+    def active(self) -> _WorksheetOrChartsheetLike | None: ...
     @active.setter
     def active(self, value: Worksheet | Chartsheet | int) -> None: ...
     # read_only workbook cannot call this method
@@ -66,18 +83,18 @@ class Workbook:
     def remove_sheet(self, worksheet: _WorkbookSheet) -> None: ...
     def create_chartsheet(self, title: str | _Decodable | None = None, index: int | None = None) -> Chartsheet: ...
     @deprecated("Use wb[sheetname]")
-    def get_sheet_by_name(self, name: str) -> _WorkbookSheet: ...
+    def get_sheet_by_name(self, name: str) -> _WorksheetOrChartsheetLike: ...
     def __contains__(self, key: str) -> bool: ...
     def index(self, worksheet: _WorkbookWorksheet) -> int: ...
     @deprecated("Use wb.index(worksheet)")
     def get_index(self, worksheet: _WorkbookWorksheet) -> int: ...
-    def __getitem__(self, key: str) -> _WorkbookSheet: ...
+    def __getitem__(self, key: str) -> _WorksheetOrChartsheetLike: ...
     def __delitem__(self, key: str) -> None: ...
-    def __iter__(self) -> Iterator[_WorkbookWorksheet]: ...
+    def __iter__(self) -> Iterator[_WorksheetLike]: ...
     @deprecated("Use wb.sheetnames")
     def get_sheet_names(self) -> list[str]: ...
     @property
-    def worksheets(self) -> list[_WorkbookWorksheet]: ...
+    def worksheets(self) -> list[_WorksheetLike]: ...
     @property
     def chartsheets(self) -> list[Chartsheet]: ...
     @property