diff --git a/setup.py b/setup.py
index fe091f16..d9b6bdb9 100644
--- a/setup.py
+++ b/setup.py
@@ -2,7 +2,6 @@
 
 """The setup script."""
 
-
 from setuptools import find_packages, setup
 
 with open("README.md") as readme_file:
diff --git a/tests/__init__.py b/tests/__init__.py
index 554896f8..61492edc 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,4 +1,5 @@
 """Unit test package for xbitinfo."""
+
 import importlib
 from distutils import version
 
diff --git a/tests/test_bitround.py b/tests/test_bitround.py
index aaa126b9..86cd195c 100644
--- a/tests/test_bitround.py
+++ b/tests/test_bitround.py
@@ -1,6 +1,4 @@
-import numpy as np
 import pytest
-import xarray as xr
 from dask import is_dask_collection
 from xarray.testing import assert_allclose, assert_equal
 
diff --git a/tests/test_get_bitinformation.py b/tests/test_get_bitinformation.py
index 0a38ca0f..68b53804 100644
--- a/tests/test_get_bitinformation.py
+++ b/tests/test_get_bitinformation.py
@@ -1,4 +1,5 @@
 """Tests for `xbitinfo` package."""
+
 import os
 
 import numpy as np
diff --git a/tests/test_get_keepbits.py b/tests/test_get_keepbits.py
index cec0b99f..cd68938a 100644
--- a/tests/test_get_keepbits.py
+++ b/tests/test_get_keepbits.py
@@ -1,11 +1,12 @@
 """Tests for `xbitinfo.get_keepbits`."""
+
 import pytest
 import xarray as xr
 
 import xbitinfo as xb
 
 
-@pytest.fixture
+@pytest.fixture()
 def rasm_info_per_bit(rasm):
     return xb.get_bitinformation(rasm, axis=0)
 
diff --git a/tests/test_save_compressed.py b/tests/test_save_compressed.py
index 09e21878..c31c0f92 100644
--- a/tests/test_save_compressed.py
+++ b/tests/test_save_compressed.py
@@ -3,7 +3,6 @@
 
 import numcodecs
 import pytest
-import xarray as xr
 import zarr
 
 import xbitinfo as xb
diff --git a/xbitinfo/_py_bitinfo.py b/xbitinfo/_py_bitinfo.py
index 620e3146..00cc7d14 100644
--- a/xbitinfo/_py_bitinfo.py
+++ b/xbitinfo/_py_bitinfo.py
@@ -1,6 +1,5 @@
 import dask.array as da
 import numpy as np
-import numpy.ma as nm
 
 
 def exponent_bias(dtype):
diff --git a/xbitinfo/bitround.py b/xbitinfo/bitround.py
index 91858b4b..34e35bd5 100644
--- a/xbitinfo/bitround.py
+++ b/xbitinfo/bitround.py
@@ -37,12 +37,12 @@ def _keepbits_interface(da, keepbits):
         else:
             raise ValueError(f"name {v} not for in keepbits: {keepbits.keys()}")
     elif isinstance(keepbits, xr.Dataset):
-        assert keepbits.coords["inflevel"].shape <= (
-            1,
+        assert (
+            keepbits.coords["inflevel"].shape <= (1,)
         ), "Information content is only allowed for one 'inflevel' here. Please make a selection."
         if "dim" in keepbits.coords:
-            assert keepbits.coords["dim"].shape <= (
-                1,
+            assert (
+                keepbits.coords["dim"].shape <= (1,)
             ), "Information content is only allowed along one dimension here. Please select one `dim`. To find the maximum keepbits, simply use `keepbits.max(dim='dim')`"
         v = da.name
         if v in keepbits.keys():
@@ -50,11 +50,11 @@ def _keepbits_interface(da, keepbits):
         else:
             raise ValueError(f"name {v} not for in keepbits: {keepbits.keys()}")
     elif isinstance(keepbits, xr.DataArray):
-        assert keepbits.coords["inflevel"].shape <= (
-            1,
+        assert (
+            keepbits.coords["inflevel"].shape <= (1,)
         ), "Information content is only allowed for one 'inflevel' here. Please make a selection."
-        assert keepbits.coords["dim"].shape <= (
-            1,
+        assert (
+            keepbits.coords["dim"].shape <= (1,)
         ), "Information content is only allowed along one dimension here. Please select one `dim`. To find the maximum keepbits, simply use `keepbits.max(dim='dim')`"
         v = da.name
         if v == keepbits.name:
@@ -176,7 +176,9 @@ def bitround_along_dim(
     >>> ds_bitrounded_along_lon = xb.bitround.bitround_along_dim(
     ...     ds, info_per_bit, dim="lon"
     ... )
-    >>> (ds - ds_bitrounded_along_lon)["air"].isel(time=0).plot()  # doctest: +ELLIPSIS
+    >>> (ds - ds_bitrounded_along_lon)["air"].isel(
+    ...     time=0
+    ... ).plot()  # doctest: +ELLIPSIS
     <matplotlib.collections.QuadMesh object at ...>
 
     """
@@ -186,14 +188,12 @@ def bitround_along_dim(
     elif inflevels is not None:
         stride = ds[dim].size // len(inflevels)
         for i, inf in enumerate(inflevels):  # last slice might be a bit larger
-            ds_slice = ds.isel(
-                {
-                    dim: slice(
-                        stride * i,
-                        stride * (i + 1) if i != len(inflevels) - 1 else None,
-                    )
-                }
-            )
+            ds_slice = ds.isel({
+                dim: slice(
+                    stride * i,
+                    stride * (i + 1) if i != len(inflevels) - 1 else None,
+                )
+            })
             keepbits_slice = get_keepbits(info_per_bit, inf)
             if inf != 1:
                 ds_slice_bitrounded = xr_bitround(ds_slice, keepbits_slice)
diff --git a/xbitinfo/graphics.py b/xbitinfo/graphics.py
index bef4037a..2aa70837 100644
--- a/xbitinfo/graphics.py
+++ b/xbitinfo/graphics.py
@@ -149,12 +149,10 @@ def add_bitinfo_labels(
 
         # write inflevel
         t = ax.text(
-            da.isel(
-                {
-                    x_dim_name: int(stride * (i + 0.5)),
-                    y_dim_name: da[y_dim_name].size // 2,
-                }
-            )[lon_coord_name].values,
+            da.isel({
+                x_dim_name: int(stride * (i + 0.5)),
+                y_dim_name: da[y_dim_name].size // 2,
+            })[lon_coord_name].values,
             label_latitude - label_latitude_offset,
             str(round(inf * 100, 2)) + "%",
             horizontalalignment="center",
@@ -166,12 +164,10 @@ def add_bitinfo_labels(
     for i, keep in enumerate(keepbits):
         # write keepbits
         t_keepbits = ax.text(
-            da.isel(
-                {
-                    x_dim_name: int(stride * (i + 0.5)),
-                    y_dim_name: da[y_dim_name].size // 2,
-                }
-            )[lon_coord_name].values,
+            da.isel({
+                x_dim_name: int(stride * (i + 0.5)),
+                y_dim_name: da[y_dim_name].size // 2,
+            })[lon_coord_name].values,
             label_latitude + label_latitude_offset,
             f"keepbits = {keep}",
             horizontalalignment="center",
@@ -420,7 +416,7 @@ def plot_bitinformation(bitinfo, cmap="turku", crop=None):
         axs[d].text(
             infbits[0] + 0.1,
             0.8,
-            f"{int(infbits[0]-nonmantissa_bits)} mantissa bits",
+            f"{int(infbits[0] - nonmantissa_bits)} mantissa bits",
             fontsize=8,
             color="saddlebrown",
         )
@@ -428,19 +424,17 @@ def plot_bitinformation(bitinfo, cmap="turku", crop=None):
             axs[d].text(
                 infbits[i] + 0.1,
                 (i) + 0.8,
-                f"{int(infbits[i]-9)}",
+                f"{int(infbits[i] - 9)}",
                 fontsize=8,
                 color="saddlebrown",
             )
 
         major_xticks = np.array([n_sign, n_sign + n_exp, n_bits], dtype="int")
         axs[d].set_xticks(major_xticks[major_xticks <= bits_to_show])
-        minor_xticks = np.hstack(
-            [
-                np.arange(n_sign, nonmantissa_bits - 1),
-                np.arange(nonmantissa_bits, n_bits - 1),
-            ]
-        )
+        minor_xticks = np.hstack([
+            np.arange(n_sign, nonmantissa_bits - 1),
+            np.arange(nonmantissa_bits, n_bits - 1),
+        ])
         axs[d].set_xticks(
             minor_xticks[minor_xticks <= bits_to_show],
             minor=True,
diff --git a/xbitinfo/save_compressed.py b/xbitinfo/save_compressed.py
index 05f8ae63..fd4ded1e 100644
--- a/xbitinfo/save_compressed.py
+++ b/xbitinfo/save_compressed.py
@@ -36,7 +36,9 @@ def get_compress_encoding_nc(
 
     Example
     -------
-    >>> ds = xr.Dataset({"Tair": (("time", "x", "y"), np.random.rand(36, 20, 10))})
+    >>> ds = xr.Dataset(
+    ...     {"Tair": (("time", "x", "y"), np.random.rand(36, 20, 10))}
+    ... )
     >>> get_compress_encoding_nc(ds)
     {'Tair': {'zlib': True, 'shuffle': True, 'complevel': 9, 'chunksizes': (36, 20, 10)}}
     >>> get_compress_encoding_nc(ds, for_cdo=True)
@@ -187,7 +189,9 @@ class ToCompressed_Zarr:
     >>> ds = xr.tutorial.load_dataset("rasm")
     >>> path = "compressed_rasm.zarr"
     >>> ds.to_compressed_zarr(path, mode="w")
-    >>> ds.to_compressed_zarr(path, compressor=numcodecs.Blosc("zlib"), mode="w")
+    >>> ds.to_compressed_zarr(
+    ...     path, compressor=numcodecs.Blosc("zlib"), mode="w"
+    ... )
     >>> ds.to_compressed_zarr(
     ...     path, compressor={"Tair": numcodecs.Blosc("zstd")}, mode="w"
     ... )
diff --git a/xbitinfo/xbitinfo.py b/xbitinfo/xbitinfo.py
index 4450a98f..5156dec9 100644
--- a/xbitinfo/xbitinfo.py
+++ b/xbitinfo/xbitinfo.py
@@ -22,7 +22,7 @@
 if not already_ran and julia_installed:
     already_ran = install(quiet=True)
     jl = Julia(compiled_modules=False, debug=False)
-    from julia import Main  # noqa: E402
+    from julia import Main
 
     path_to_julia_functions = os.path.join(
         os.path.dirname(__file__), "bitinformation_wrapper.jl"
@@ -105,7 +105,7 @@ def dict_to_dataset(info_per_bit):
     return dsb
 
 
-def get_bitinformation(  # noqa: C901
+def get_bitinformation(
     ds,
     dim=None,
     axis=None,
@@ -273,7 +273,7 @@ def _jl_get_bitinformation(ds, var, axis, dim, kwargs={}):
             axis_jl = ds[var].get_axis_num(dim) + 1
         except ValueError:
             logging.info(f"Variable {var} does not have dimension {dim}. Skipping.")
-            return
+            return None
     assert isinstance(axis_jl, int)
     Main.dim = axis_jl
     kwargs_str = _get_bitinformation_kwargs_handler(ds[var], kwargs)
@@ -314,7 +314,7 @@ def _py_get_bitinformation(ds, var, axis, dim, kwargs={}):
             axis = ds[var].get_axis_num(dim)
         except ValueError:
             logging.info(f"Variable {var} does not have dimension {dim}. Skipping.")
-            return
+            return None
     info_per_bit = {}
     logging.info("Calling python implementation now")
     info_per_bit["bitinfo"] = pb.bitinformation(X, axis=axis).compute()
@@ -378,11 +378,13 @@ def load_bitinformation(label):
     label_file = label + ".json"
     if os.path.exists(label_file):
         with open(label_file) as f:
-            logging.debug(f"Load bitinformation from {label+'.json'}")
+            logging.debug(f"Load bitinformation from {label + '.json'}")
             info_per_bit = json.load(f)
         return dict_to_dataset(info_per_bit)
     else:
-        raise FileNotFoundError(f"No bitinformation could be found at {label+'.json'}")
+        raise FileNotFoundError(
+            f"No bitinformation could be found at {label + '.json'}"
+        )
 
 
 def get_keepbits(info_per_bit, inflevel=0.99):