Ignore MyPy errors caused by DepthFirstIterator not being detected as iterator

MyPy is wrong in this case.

Contributes to issue CURA-5330.

cura/Settings/ExtruderManager.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 from PyQt5.QtCore import pyqtSignal, pyqtProperty, QObject, QVariant  # For communicating data and events to Qt.
@@ -136,7 +136,7 @@ class ExtruderManager(QObject):
             selected_nodes = []
             for node in Selection.getAllSelectedObjects():
                 if node.callDecoration("isGroup"):
-                    for grouped_node in BreadthFirstIterator(node):
+                    for grouped_node in BreadthFirstIterator(node): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
                         if grouped_node.callDecoration("isGroup"):
                             continue
 
@@ -265,7 +265,7 @@ class ExtruderManager(QObject):
             return []
 
         # Get the extruders of all printable meshes in the scene
-        meshes = [node for node in DepthFirstIterator(scene_root) if isinstance(node, SceneNode) and node.isSelectable()]
+        meshes = [node for node in DepthFirstIterator(scene_root) if isinstance(node, SceneNode) and node.isSelectable()] #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
         for mesh in meshes:
             extruder_stack_id = mesh.callDecoration("getActiveExtruder")
             if not extruder_stack_id: