graphlib: add in py39 (#4268)

Co-authored-by: hauntsaninja <>

stdlib/3.9/graphlib.pyi

@@ -0,0 +1,15 @@
+from typing import Generic, Iterable, Mapping, Optional, Tuple, TypeVar
+
+_T = TypeVar("_T")
+
+class TopologicalSorter(Generic[_T]):
+    def __init__(self, graph: Optional[Mapping[_T, Iterable[_T]]] = ...) -> None: ...
+    def add(self, node: _T, *predecessors: _T) -> None: ...
+    def prepare(self) -> None: ...
+    def is_active(self) -> bool: ...
+    def __bool__(self) -> bool: ...
+    def done(self, *nodes: _T) -> None: ...
+    def get_ready(self) -> Tuple[_T, ...]: ...
+    def static_order(self) -> Iterable[_T]: ...
+
+class CycleError(ValueError): ...