Fix Widget.{draw,demo}

Author: srittau

stubs/reportlab/reportlab/graphics/widgetbase.pyi

@@ -1,4 +1,5 @@
 from _typeshed import Incomplete
+from abc import abstractmethod
 from typing import Final
 
 from reportlab.graphics import shapes
@@ -15,9 +16,10 @@ class PropHolder:
     def dumpProperties(self, prefix: str = "") -> None: ...
 
 class Widget(PropHolder, shapes.UserNode):
-    # TODO: draw should probably be marked abstract
-    def draw(self) -> None: ...
-    def demo(self) -> None: ...
+    @abstractmethod
+    def draw(self): ...
+    @abstractmethod
+    def demo(self): ...
     def provideNode(self) -> shapes.Shape: ...
     def getBounds(self) -> tuple[float, float, float, float]: ...