diff --git a/cura/Arranging/ShapeArray.py b/cura/Arranging/ShapeArray.py
index 5607c03663..714d9d3837 100644
--- a/cura/Arranging/ShapeArray.py
+++ b/cura/Arranging/ShapeArray.py
@@ -74,14 +74,14 @@ class ShapeArray:
         # If the child-nodes are included, adjust convex hulls as well:
         if include_children:
             children = node.getAllChildren()
-            if not children is None:
+            if children is not None:
                 for child in children:
                     # 'Inefficient' combination of convex hulls through known code rather than mess it up:
                     child_hull = child.callDecoration("getConvexHull")
-                    if not child_hull is None:
+                    if child_hull is not None:
                         hull_verts = hull_verts.unionConvexHulls(child_hull)
                     child_hull_head = child.callDecoration("getConvexHullHead") or child_hull
-                    if not child_hull_head is None:
+                    if child_hull_head is not None:
                         hull_head_verts = hull_head_verts.unionConvexHulls(child_hull_head)
 
         offset_verts = hull_head_verts.getMinkowskiHull(Polygon.approximatedCircle(min_offset))
@@ -159,4 +159,4 @@ class ShapeArray:
 
         max_col_idx = (idxs[0] - p1[0]) / (p2[0] - p1[0]) * (p2[1] - p1[1]) + p1[1]
         sign = numpy.sign(p2[0] - p1[0])
-        return idxs[1] * sign <= max_col_idx * sign
\ No newline at end of file
+        return idxs[1] * sign <= max_col_idx * sign