diff --git a/tests/test_tree.py b/tests/test_tree.py
index 719fe78..287b734 100644
--- a/tests/test_tree.py
+++ b/tests/test_tree.py
@@ -555,12 +555,12 @@ def tearDown(self):
 
     def test_show_without_sorting(self):
         t = Tree()
-        t.create_node('Students', 'Students', parent=None)
-        Node(tag='Students', identifier='Students', data=None)
-        t.create_node('Ben', 'Ben',parent='Students')
-        Node(tag='Ben', identifier='Ben', data=None)
-        t.create_node('Annie', 'Annie',parent='Students')
-        Node(tag='Annie', identifier='Annie', data=None)
+        t.create_node("Students", "Students", parent=None)
+        Node(tag="Students", identifier="Students", data=None)
+        t.create_node("Ben", "Ben", parent="Students")
+        Node(tag="Ben", identifier="Ben", data=None)
+        t.create_node("Annie", "Annie", parent="Students")
+        Node(tag="Annie", identifier="Annie", data=None)
         t.show()
         self.assertEqual(
             t.show(sorting=False, stdout=False),
diff --git a/treelib/tree.py b/treelib/tree.py
index 908db4e..7d92297 100644
--- a/treelib/tree.py
+++ b/treelib/tree.py
@@ -222,7 +222,9 @@ def key(node):
                 return node
 
         # iter with func
-        for pre, node in self.__get(nid, level, filter, key, reverse, line_type, sorting):
+        for pre, node in self.__get(
+            nid, level, filter, key, reverse, line_type, sorting
+        ):
             label = get_label(node)
             func("{0}{1}".format(pre, label).encode("utf-8"))