diff --git a/pre_commit_hooks/string_fixer_for_jupyter_notebooks.py b/pre_commit_hooks/string_fixer_for_jupyter_notebooks.py
index 1ab47f4..f363d57 100644
--- a/pre_commit_hooks/string_fixer_for_jupyter_notebooks.py
+++ b/pre_commit_hooks/string_fixer_for_jupyter_notebooks.py
@@ -30,8 +30,8 @@ def fix_strings(filename: str) -> int:
                 if fixed != source_in_1_line:
                     fixed_lines = fixed.split('\n')
                     cell['source'] = (
-                            [_ + '\n' for _ in fixed_lines[:-1]]
-                            + [fixed_lines[-1]]
+                        [_ + '\n' for _ in fixed_lines[:-1]] +
+                        [fixed_lines[-1]]
                     )
                     return_value = 1
 
@@ -41,7 +41,7 @@ def fix_strings(filename: str) -> int:
                 json.dump(notebook_contents, f, indent=1)
                 # Jupyter notebooks (.ipynb) always ends with a new line
                 # but json.dump does not.
-                f.write("\n")
+                f.write('\n')
 
         return return_value
 
diff --git a/tests/string_fixer_for_jupyter_notebooks_test.py b/tests/string_fixer_for_jupyter_notebooks_test.py
index f86fec9..e04efd2 100644
--- a/tests/string_fixer_for_jupyter_notebooks_test.py
+++ b/tests/string_fixer_for_jupyter_notebooks_test.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pre_commit_hooks.string_fixer_for_jupyter_notebooks import main
@@ -10,6 +12,7 @@ TESTS = (
     ('jupyter_case_2.ipynb', 'jupyter_case_2.ipynb', 0),
 )
 
+
 @pytest.mark.parametrize(('input_file', 'output_file', 'expected_retv'), TESTS)
 def test_rewrite(input_file, output_file, expected_retv, tmpdir):
     with open(get_resource_path(input_file)) as f: