diff --git a/reciprocalspaceship/io/dials.py b/reciprocalspaceship/io/dials.py
index 56918f55..b3b075aa 100644
--- a/reciprocalspaceship/io/dials.py
+++ b/reciprocalspaceship/io/dials.py
@@ -181,9 +181,9 @@ def _read_dials_stills_ray(fnames, unitcell, spacegroup, numjobs=10, extra_cols=
 
 def dials_to_mtz_dtypes(ds, inplace=True):
     """
-    Coerce the dtypes in ds into ones that can be written to an mtz file. 
+    Coerce the dtypes in ds into ones that can be written to an mtz file.
     This will downcast doubles to single precision. If "variance" columns
-    are present, they will be converted to "sigma" and assigned 
+    are present, they will be converted to "sigma" and assigned
     StandardDeviationDtype.
 
     Parameters
@@ -226,7 +226,7 @@ def read_dials_stills(
     """
     Read reflections from still images processed by DIALS from fnames and return
     them as a DataSet. By default, this function will not convert the data from
-    dials into an MTZ compatible format. 
+    dials into an MTZ compatible format.
 
     Parameters
     ----------
diff --git a/tests/io/test_dials.py b/tests/io/test_dials.py
index 8541b2d9..e042cc59 100644
--- a/tests/io/test_dials.py
+++ b/tests/io/test_dials.py
@@ -101,6 +101,7 @@ def make_refls(unit_cell, sg, seed=8675309, file_prefix=""):
     ds0.set_index(["H", "K", "L"], inplace=True, drop=True)
     return ds0, pack_names
 
+
 def test_dials_mtz_conversion():
     unit_cell = 78, 78, 235, 90, 90, 120
     sg = "P 65 2 2"
@@ -109,16 +110,23 @@ def test_dials_mtz_conversion():
         prefix = tdir + "/"
         ds0, pack_names = make_refls(unit_cell, sg, file_prefix=prefix)
         ds = read_dials_stills(
-            pack_names, unit_cell, sg, parallel_backend=None, numjobs=1, verbose=False, mtz_dtypes=True
+            pack_names,
+            unit_cell,
+            sg,
+            parallel_backend=None,
+            numjobs=1,
+            verbose=False,
+            mtz_dtypes=True,
         )
 
-        mtzout = tdir + '/ds.mtz'
+        mtzout = tdir + "/ds.mtz"
         ds.write_mtz(mtzout)
         assert os.path.exists(mtzout)
         test_ds = rs.read_mtz(mtzout).reset_index()
         for k in ds:
             assert np.allclose(ds[k], test_ds[k])
 
+
 @pytest.mark.parametrize("parallel_backend", ["mpi", "ray"])
 @pytest.mark.parametrize("mtz_dtypes", [True, False])
 def test_dials_reader(parallel_backend, mtz_dtypes, verbose=False):
@@ -134,7 +142,13 @@ def test_dials_reader(parallel_backend, mtz_dtypes, verbose=False):
         ds0, pack_names = make_refls(unit_cell, sg, file_prefix=prefix)
         # read without parallelization
         ds1 = read_dials_stills(
-            pack_names, unit_cell, sg, parallel_backend=None, numjobs=1, verbose=verbose, mtz_dtypes=mtz_dtypes
+            pack_names,
+            unit_cell,
+            sg,
+            parallel_backend=None,
+            numjobs=1,
+            verbose=verbose,
+            mtz_dtypes=mtz_dtypes,
         )
         gemmi_unit_cell = gemmi.UnitCell(*unit_cell)
         gemmi_sg = gemmi.SpaceGroup(sg)