diff --git a/src/spgrep_modulation/__init__.py b/src/spgrep_modulation/__init__.py
index 2664304..d803d6b 100644
--- a/src/spgrep_modulation/__init__.py
+++ b/src/spgrep_modulation/__init__.py
@@ -1,4 +1,5 @@
 """Modulation analysis with irreps and isotropy subgroups."""
+
 from importlib.metadata import PackageNotFoundError, version
 
 # https://github.com/pypa/setuptools_scm/#retrieving-package-version-at-runtime
diff --git a/src/spgrep_modulation/irreps.py b/src/spgrep_modulation/irreps.py
index 4420200..a3adcc4 100644
--- a/src/spgrep_modulation/irreps.py
+++ b/src/spgrep_modulation/irreps.py
@@ -1,4 +1,5 @@
 """Irreps for phonon."""
+
 from __future__ import annotations
 
 from typing import Literal
diff --git a/src/spgrep_modulation/isotropy.py b/src/spgrep_modulation/isotropy.py
index 7389f45..f296dce 100644
--- a/src/spgrep_modulation/isotropy.py
+++ b/src/spgrep_modulation/isotropy.py
@@ -1,4 +1,5 @@
 """Isotropy subgroup of space group."""
+
 from __future__ import annotations
 
 from fractions import Fraction
diff --git a/src/spgrep_modulation/modulation.py b/src/spgrep_modulation/modulation.py
index 96eb14c..cd42ab3 100644
--- a/src/spgrep_modulation/modulation.py
+++ b/src/spgrep_modulation/modulation.py
@@ -1,4 +1,5 @@
 """Modulation class."""
+
 from __future__ import annotations
 
 from warnings import warn
diff --git a/src/spgrep_modulation/utils.py b/src/spgrep_modulation/utils.py
index 8654321..e0f6696 100644
--- a/src/spgrep_modulation/utils.py
+++ b/src/spgrep_modulation/utils.py
@@ -1,4 +1,5 @@
 """Utility functions."""
+
 from __future__ import annotations
 
 from fractions import Fraction
diff --git a/src/spgrep_modulation/visualize.py b/src/spgrep_modulation/visualize.py
index 5989840..5455d84 100644
--- a/src/spgrep_modulation/visualize.py
+++ b/src/spgrep_modulation/visualize.py
@@ -1,4 +1,5 @@
 """Utilities for visualization in notebook."""
+
 from __future__ import annotations
 
 import math