Make inspect.getblock more ergonomic for common input types (#10920)

stdlib/inspect.pyi

@@ -294,6 +294,14 @@ _SourceObjectType: TypeAlias = (
 
 def findsource(object: _SourceObjectType) -> tuple[list[str], int]: ...
 def getabsfile(object: _SourceObjectType, _filename: str | None = None) -> str: ...
+
+# Special-case the two most common input types here
+# to avoid the annoyingly vague `Sequence[str]` return type
+@overload
+def getblock(lines: list[str]) -> list[str]: ...
+@overload
+def getblock(lines: tuple[str, ...]) -> tuple[str, ...]: ...
+@overload
 def getblock(lines: Sequence[str]) -> Sequence[str]: ...
 def getdoc(object: object) -> str | None: ...
 def getcomments(object: object) -> str | None: ...