diff --git a/discretisedfield/__init__.py b/discretisedfield/__init__.py
index 6251a144..98857919 100644
--- a/discretisedfield/__init__.py
+++ b/discretisedfield/__init__.py
@@ -1,4 +1,5 @@
 """Finite-difference fields."""
+
 import importlib.metadata
 import pathlib
 
diff --git a/discretisedfield/field.py b/discretisedfield/field.py
index a291d8ba..88a8d15f 100644
--- a/discretisedfield/field.py
+++ b/discretisedfield/field.py
@@ -601,7 +601,7 @@ def vdim_mapping(self, vdim_mapping):
     def _r_dim_mapping(self):
         """Map dims to vdims."""
         reversed_mapping = {val: key for key, val in self.vdim_mapping.items()}
-        return {dim: reversed_mapping.get(dim, None) for dim in self.mesh.region.dims}
+        return {dim: reversed_mapping.get(dim) for dim in self.mesh.region.dims}
 
     def __abs__(self):
         """Absolute value of the field.
diff --git a/discretisedfield/io/__init__.py b/discretisedfield/io/__init__.py
index 2076b57b..3346626c 100644
--- a/discretisedfield/io/__init__.py
+++ b/discretisedfield/io/__init__.py
@@ -5,6 +5,7 @@
 and :py:func:`discretisedfield.Field.fromfile` instead.
 
 """
+
 import json
 import pathlib
 
diff --git a/discretisedfield/io/ovf2vtk.py b/discretisedfield/io/ovf2vtk.py
index c2ae7c1c..b144d695 100644
--- a/discretisedfield/io/ovf2vtk.py
+++ b/discretisedfield/io/ovf2vtk.py
@@ -1,4 +1,5 @@
 """OVF to VTK file conversion."""
+
 import argparse
 
 import discretisedfield as df
diff --git a/discretisedfield/plotting/__init__.py b/discretisedfield/plotting/__init__.py
index 3ad09ae3..b3eb2094 100644
--- a/discretisedfield/plotting/__init__.py
+++ b/discretisedfield/plotting/__init__.py
@@ -1,4 +1,5 @@
 """Matplotlib based plotting."""
+
 # ruff: noqa: F401
 from discretisedfield.plotting import util
 from discretisedfield.plotting.hv import Hv
diff --git a/discretisedfield/plotting/hv.py b/discretisedfield/plotting/hv.py
index a7178931..0c6d3d0c 100644
--- a/discretisedfield/plotting/hv.py
+++ b/discretisedfield/plotting/hv.py
@@ -1,4 +1,5 @@
 """Holoviews-based plotting."""
+
 import contextlib
 import copy
 import functools
diff --git a/discretisedfield/plotting/k3d_field.py b/discretisedfield/plotting/k3d_field.py
index bcd71218..88e41dd7 100644
--- a/discretisedfield/plotting/k3d_field.py
+++ b/discretisedfield/plotting/k3d_field.py
@@ -1,4 +1,5 @@
 """K3d based plotting."""
+
 import k3d
 import matplotlib
 import numpy as np
diff --git a/discretisedfield/plotting/mpl.py b/discretisedfield/plotting/mpl.py
index 6078d4b1..2b96688d 100644
--- a/discretisedfield/plotting/mpl.py
+++ b/discretisedfield/plotting/mpl.py
@@ -1,4 +1,5 @@
 """Matplotlib-based plotting."""
+
 import abc
 
 import matplotlib.pyplot as plt
diff --git a/discretisedfield/plotting/mpl_field.py b/discretisedfield/plotting/mpl_field.py
index 56e3be37..2bb9ab51 100644
--- a/discretisedfield/plotting/mpl_field.py
+++ b/discretisedfield/plotting/mpl_field.py
@@ -1,4 +1,5 @@
 """Matplotlib-based plotting."""
+
 import warnings
 
 import matplotlib.pyplot as plt
diff --git a/discretisedfield/tools/__init__.py b/discretisedfield/tools/__init__.py
index d63619a6..4d7e989a 100644
--- a/discretisedfield/tools/__init__.py
+++ b/discretisedfield/tools/__init__.py
@@ -1,4 +1,5 @@
 """Convenience tools"""
+
 # ruff: noqa: F401
 from .tools import (
     count_bps,
diff --git a/tasks.py b/tasks.py
index e8b7c286..87849430 100644
--- a/tasks.py
+++ b/tasks.py
@@ -1,4 +1,5 @@
 """Tasks to release the package."""
+
 import os
 import shutil