Fix code style and typing

cura/Machines/Models/CustomQualityProfilesDropDownMenuModel.py

@@ -7,10 +7,12 @@ import cura.CuraApplication  # Imported this way to prevent circular references.
 from cura.Machines.ContainerTree import ContainerTree
 from cura.Machines.Models.QualityProfilesDropDownMenuModel import QualityProfilesDropDownMenuModel
 
+
 ##  This model is used for the custom profile items in the profile drop down
 #   menu.
 class CustomQualityProfilesDropDownMenuModel(QualityProfilesDropDownMenuModel):
-    def _update(self):
+
+    def _update(self) -> None:
         Logger.log("d", "Updating {model_class_name}.".format(model_class_name = self.__class__.__name__))
 
         active_global_stack = cura.CuraApplication.CuraApplication.getInstance().getMachineManager().activeMachine

cura/Machines/QualityChangesGroup.py

@@ -10,7 +10,8 @@ from typing import Any, Dict, Optional
 #   contains an instance container for the global stack and one instance
 #   container per extruder.
 class QualityChangesGroup(QObject):
-    def __init__(self, name: str, quality_type: str, intent_category: str, parent = None) -> None:
+
+    def __init__(self, name: str, quality_type: str, intent_category: str, parent: Optional["QObject"] = None) -> None:
         super().__init__(parent)
         self.name = name
         self.quality_type = quality_type