Move existNetworkInstances into discover action

cura/Settings/MachineManager.py

@@ -1455,13 +1455,6 @@ class MachineManager(QObject):
         if self.hasUserSettings and self._application.getPreferences().getValue("cura/active_mode") == 1:
             self._application.discardOrKeepProfileChanges()
 
-
-    ##  This method checks if there is an instance connected to the given network_key
-    def existNetworkInstances(self, network_key: str) -> bool:
-        metadata_filter = {"um_network_key": network_key}
-        containers = CuraContainerRegistry.getInstance().findContainerStacks(type = "machine", **metadata_filter)
-        return bool(containers)
-
     @pyqtSlot("QVariant")
     def setGlobalVariant(self, container_node: "ContainerNode") -> None:
         self.blurSettings.emit()

plugins/UM3NetworkPrinting/src/DiscoverUM3Action.py

@@ -157,7 +157,9 @@ class DiscoverUM3Action(MachineAction):
 
     @pyqtSlot(str, result = bool)
     def existsKey(self, key: str) -> bool:
-        return CuraApplication.getInstance().getMachineManager().existNetworkInstances(network_key = key)
+        metadata_filter = {"um_network_key": key}
+        containers = CuraContainerRegistry.getInstance().findContainerStacks(type="machine", **metadata_filter)
+        return bool(containers)
 
     @pyqtSlot()
     def loadConfigurationFromPrinter(self) -> None: