Fixed type hinting for Extruder stack

cura/Settings/ExtruderStack.py

@@ -1,7 +1,7 @@
 # Copyright (c) 2017 Ultimaker B.V.
 # Cura is released under the terms of the AGPLv3 or higher.
 
-from typing import Any
+from typing import Any, TYPE_CHECKING, Optional
 
 from PyQt5.QtCore import pyqtProperty, pyqtSignal, pyqtSlot
 
@@ -17,6 +17,9 @@ from . import Exceptions
 from .CuraContainerStack import CuraContainerStack
 from .ExtruderManager import ExtruderManager
 
+if TYPE_CHECKING:
+    from cura.Settings.GlobalStack import GlobalStack
+
 ##  Represents an Extruder and its related containers.
 #
 #
@@ -38,6 +41,10 @@ class ExtruderStack(CuraContainerStack):
         # For backward compatibility: Register the extruder with the Extruder Manager
         ExtruderManager.getInstance().registerExtruder(self, stack.id)
 
+    @override(ContainerStack)
+    def getNextStack(self) -> Optional["GlobalStack"]:
+        return super().getNextStack()
+
     @classmethod
     def getLoadingPriority(cls) -> int:
         return 3