diff --git a/org_rw/org_rw.py b/org_rw/org_rw.py
index 7133ad9..ddb88ec 100644
--- a/org_rw/org_rw.py
+++ b/org_rw/org_rw.py
@@ -1,4 +1,5 @@
 from __future__ import annotations
+
 import collections
 import difflib
 import logging
@@ -7,7 +8,6 @@ import re
 import sys
 from datetime import date, datetime, timedelta
 from enum import Enum
-
 from typing import (
     Dict,
     Iterator,
@@ -860,7 +860,9 @@ class Headline:
         # No need to finalize as we can take the data from the reader instead of from a doc
         if len(reader.headlines) > 0:
             # Probably can be done by just adding the headlines to this one's children
-            raise NotImplementedError('new headlines on raw contents not supported yet. This probably should be simple, see comment on code.')
+            raise NotImplementedError(
+                "new headlines on raw contents not supported yet. This probably should be simple, see comment on code."
+            )
 
         for kw in reader.keywords:
             self.keywords.append(offset_linenum(self.start_line + 1, kw))
@@ -879,7 +881,6 @@ class Headline:
 
         # Environment is not used, as it's known
 
-
     def get_element_in_line(self, linenum):
         for line in self.contents:
             if linenum == line.linenum:
@@ -1077,9 +1078,7 @@ Keyword = collections.namedtuple(
 Property = collections.namedtuple(
     "Property", ("linenum", "match", "key", "value", "options")
 )
-Structural = collections.namedtuple(
-    "Structural", ("linenum", "line")
-)
+Structural = collections.namedtuple("Structural", ("linenum", "line"))
 
 
 class ListItem:
@@ -1129,13 +1128,16 @@ TableRow = collections.namedtuple(
 )
 
 ItemWithLineNum = Union[Keyword, RawLine, Property, ListItem, Structural]
+
+
 def offset_linenum(offset: int, item: ItemWithLineNum) -> ItemWithLineNum:
     if isinstance(item, ListItem):
         item.linenum += offset
         return item
 
-    assert isinstance(item, (Keyword, RawLine, Property, Structural)), \
-        "Expected (Keyword|RawLine|Property|Structural), found {}".format(item)
+    assert isinstance(
+        item, (Keyword, RawLine, Property, Structural)
+    ), "Expected (Keyword|RawLine|Property|Structural), found {}".format(item)
     return item._replace(linenum=item.linenum + offset)
 
 
diff --git a/tests/test_org.py b/tests/test_org.py
index 959d968..cb204f6 100644
--- a/tests/test_org.py
+++ b/tests/test_org.py
@@ -903,8 +903,8 @@ class TestSerde(unittest.TestCase):
 
         # Update
         lines = list(doc.dump_headline(hl, recursive=False))
-        assert lines[0].startswith('* ')  # Title, skip it
-        content = '\n'.join(lines[1:])
+        assert lines[0].startswith("* ")  # Title, skip it
+        content = "\n".join(lines[1:])
         hl.update_raw_contents(content)
 
         # Check after update
@@ -914,7 +914,7 @@ class TestSerde(unittest.TestCase):
         with open(os.path.join(DIR, "13-update-reparse-test.org")) as f:
             doc = load(f)
 
-        expected_hl_contents = '''  :PROPERTIES:
+        expected_hl_contents = """  :PROPERTIES:
   :ID:       13-update-reparse-first-level-id
   :CREATED:  [2020-01-01 Wed 01:01]
   :END:
@@ -924,12 +924,12 @@ class TestSerde(unittest.TestCase):
     - With a sublist
 
   Something after the list.
-'''
+"""
 
         hl = doc.getTopHeadlines()[0]
         lines = list(doc.dump_headline(hl, recursive=False))
-        assert lines[0].startswith('* ')  # Title, skip it
-        content = '\n'.join(lines[1:])
+        assert lines[0].startswith("* ")  # Title, skip it
+        content = "\n".join(lines[1:])
         self.assertEqual(content, expected_hl_contents)
 
         # Check after update
@@ -937,17 +937,17 @@ class TestSerde(unittest.TestCase):
         self.assertEqual(content, expected_hl_contents)
 
         # Check after dump and reload
-        with tempfile.NamedTemporaryFile('wt') as f:
+        with tempfile.NamedTemporaryFile("wt") as f:
             save = org_rw.dumps(doc)
             f.write(save)
             f.flush()
 
-            with open(f.name, 'rt') as reader:
+            with open(f.name, "rt") as reader:
                 reloaded = org_rw.load(reader)
                 re_hl = reloaded.getTopHeadlines()[0]
                 lines = list(doc.dump_headline(hl, recursive=False))
-                assert lines[0].startswith('* ')  # Title, skip it
-                content = '\n'.join(lines[1:])
+                assert lines[0].startswith("* ")  # Title, skip it
+                content = "\n".join(lines[1:])
                 self.assertEqual(content, expected_hl_contents)
 
     def test_mimic_write_file_13(self):
diff --git a/tests/utils/assertions.py b/tests/utils/assertions.py
index 011c255..47ab637 100644
--- a/tests/utils/assertions.py
+++ b/tests/utils/assertions.py
@@ -67,7 +67,12 @@ class HL:
         self.content = content
         self.children = children
 
-    def assert_matches(self, test_case: unittest.TestCase, doc, accept_trailing_whitespace_changes=False):
+    def assert_matches(
+        self,
+        test_case: unittest.TestCase,
+        doc,
+        accept_trailing_whitespace_changes=False,
+    ):
         test_case.assertEqual(self.title, get_raw(doc.title))
 
         # Check properties
@@ -85,7 +90,9 @@ class HL:
                     )
 
         if accept_trailing_whitespace_changes:
-            test_case.assertEqual(get_raw_contents(doc).rstrip(), self.get_raw().rstrip())
+            test_case.assertEqual(
+                get_raw_contents(doc).rstrip(), self.get_raw().rstrip()
+            )
         else:
             test_case.assertEqual(get_raw_contents(doc), self.get_raw())