Add type hint for linecache.cache dict (#5805)

stdlib/linecache.pyi

@@ -1,10 +1,16 @@
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, List, Protocol, Tuple
 
 _ModuleGlobals = Dict[str, Any]
+_ModuleMetadata = Tuple[int, float, List[str], str]
 
-def getline(filename: str, lineno: int, module_globals: Optional[_ModuleGlobals] = ...) -> str: ...
+class _SourceLoader(Protocol):
+    def __call__(self) -> str | None: ...
+
+cache: Dict[str, _SourceLoader | _ModuleMetadata]
+
+def getline(filename: str, lineno: int, module_globals: _ModuleGlobals | None = ...) -> str: ...
 def clearcache() -> None: ...
-def getlines(filename: str, module_globals: Optional[_ModuleGlobals] = ...) -> List[str]: ...
-def checkcache(filename: Optional[str] = ...) -> None: ...
-def updatecache(filename: str, module_globals: Optional[_ModuleGlobals] = ...) -> List[str]: ...
+def getlines(filename: str, module_globals: _ModuleGlobals | None = ...) -> List[str]: ...
+def checkcache(filename: str | None = ...) -> None: ...
+def updatecache(filename: str, module_globals: _ModuleGlobals | None = ...) -> List[str]: ...
 def lazycache(filename: str, module_globals: _ModuleGlobals) -> bool: ...