From d06ce211ff0c357129ebe841f4681d6c46ac9596 Mon Sep 17 00:00:00 2001
From: Ghostkeeper <rubend@tutanota.com>
Date: Thu, 22 Aug 2019 16:47:57 +0200
Subject: [PATCH] Document new requirement that there must always be one child

Contributes to issue CURA-6600.
---
 cura/Machines/ContainerTree.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/cura/Machines/ContainerTree.py b/cura/Machines/ContainerTree.py
index e069734ef7..67e5d9fe62 100644
--- a/cura/Machines/ContainerTree.py
+++ b/cura/Machines/ContainerTree.py
@@ -20,6 +20,11 @@ if TYPE_CHECKING:
 #
 #   The tree starts at the machine definitions. For every distinct definition
 #   there will be one machine node here.
+#
+#   All of the fallbacks for material choices, quality choices, etc. should be
+#   encoded in this tree. There must always be at least one child node (for
+#   nodes that have children) but that child node may be a node representing the
+#   empty instance container.
 class ContainerTree:
     __instance = None