From ab69ca3fe2936532c80e51ad734d3f72039a1700 Mon Sep 17 00:00:00 2001
From: Pavel 'LEdoian' Turinsky <ledoian@matfyz.cz>
Date: Wed, 18 Mar 2020 21:56:25 +0100
Subject: [PATCH] Fix safe_father_of_first

---
 seminar/treelib.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/seminar/treelib.py b/seminar/treelib.py
index cfb49d86..def0f6da 100644
--- a/seminar/treelib.py
+++ b/seminar/treelib.py
@@ -20,7 +20,11 @@ def safe_pred(node):
 
 # A to samé pro .father_of_first
 def safe_father_of_first(node):
-		return node.prev
+	first_brother = node
+	while safe_pred(first_brother) is not None:
+		first_brother = safe_pred(first_brother)
+	try:
+		return first_brother.father_of_first
 	except ObjectDoesNotExist:
 		return None