diff --git a/km3io/utils/extract_dom_rates.py b/km3io/utils/extract_dom_rates.py
index 2253435b3ebfe5499fcc7a671cbd60d6e7d2036b..58f3620f00a4422862a50c1b3118afd3ebdb1c12 100644
--- a/km3io/utils/extract_dom_rates.py
+++ b/km3io/utils/extract_dom_rates.py
@@ -17,32 +17,35 @@ import os
 import numpy as np
 import h5py
 
+
 def create_matrix(dom_ids, dom_rates, dom_map):
     rows = len(dom_map)
     columns = len(dom_rates)
-    matrix = np.zeros((rows,columns))
-    for i, (rates, doms) in enumerate(zip(dom_rates,dom_ids)):
-        for r,d in zip(rates,doms):
+    matrix = np.zeros((rows, columns))
+    for i, (rates, doms) in enumerate(zip(dom_rates, dom_ids)):
+        for r, d in zip(rates, doms):
             row = dom_map[d]
-            matrix[row][i]=r
+            matrix[row][i] = r
     return matrix
 
+
 def append_to_hdf5(file, doms_rates_matrix, frame_indices, frame_times, index2dom):
     for i, row in enumerate(doms_rates_matrix):
         dataset = file[str(index2dom[i])]
         chunk_size = len(row)
-        dataset.resize(dataset.shape[0]+chunk_size, axis=0)
+        dataset.resize(dataset.shape[0] + chunk_size, axis=0)
         dataset[-chunk_size:] = row
-        
+
     frame_indices_dataset = file["frame_indices"]
     chunk_size = len(frame_indices)
-    frame_indices_dataset.resize(frame_indices_dataset.shape[0]+chunk_size, axis=0)
+    frame_indices_dataset.resize(frame_indices_dataset.shape[0] + chunk_size, axis=0)
     dataset[-chunk_size:] = frame_indices
     frame_times_dataset = file["frame_times"]
     chunk_size = len(frame_times)
-    frame_times_dataset.resize(frame_times_dataset.shape[0]+chunk_size, axis=0)
+    frame_times_dataset.resize(frame_times_dataset.shape[0] + chunk_size, axis=0)
     dataset[-chunk_size:] = frame_times
 
+
 def main():
     arguments = docopt(__doc__)
 
@@ -56,8 +59,8 @@ def main():
     dom2index = {}
     index2dom = {}
     for idx, dom in enumerate(detector.dom_ids):
-        dom2index[dom]=idx
-        index2dom[idx]=dom
+        dom2index[dom] = idx
+        index2dom[idx] = dom
 
     # Create output file and datasets
     h5 = h5py.File(data["output_file"], "a")
@@ -67,18 +70,25 @@ def main():
     h5.create_dataset("frame_indices", (0,), maxshape=(None,))
 
     # Read the channel rates from the summary slices, calculate the total module rates, and save them to the output file
-    reader = km3io.online.SummarysliceReader(data["input_file"],10000)
-    
+    reader = km3io.online.SummarysliceReader(data["input_file"], 10000)
+
     for ss_chunk in reader:
         frame_indices = ss_chunk.headers.frame_index
-        frame_times = ss_chunk.headers.UTC_seconds * 1e9 + ss_chunk.headers.UTC_16nanosecondcycles * 16
-        raw_rates = [km3io.online.get_rate(getattr(ss_chunk.slices, f"ch{ch}")) for ch in range(31)]
+        frame_times = (
+            ss_chunk.headers.UTC_seconds * 1e9
+            + ss_chunk.headers.UTC_16nanosecondcycles * 16
+        )
+        raw_rates = [
+            km3io.online.get_rate(getattr(ss_chunk.slices, f"ch{ch}"))
+            for ch in range(31)
+        ]
         dom_ids = ss_chunk.slices.dom_id
         dom_rates = np.zeros_like(raw_rates[0])
         for ch in range(31):
-            dom_rates=np.add(dom_rates, raw_rates[ch])
+            dom_rates = np.add(dom_rates, raw_rates[ch])
         m = create_matrix(dom_ids, dom_rates, dom2index)
         append_to_hdf5(h5, m, frame_indices, frame_times, index2dom)
 
+
 if __name__ == "__main__":
     main()
diff --git a/tests/test_online.py b/tests/test_online.py
index e7efc6ec6d5727a4201baf51ee722bfcdeb73100..8684f6c41e4e97e1bb71d1801956372d5210f615 100644
--- a/tests/test_online.py
+++ b/tests/test_online.py
@@ -785,7 +785,6 @@ class TestSummarysliceReader(unittest.TestCase):
         assert first_frame_index == sr[0].headers[0].frame_index
         assert last_frame_index == sr[1].headers[0].frame_index
 
-
         assert last_frame_index == sr[-1].headers[0].frame_index
         assert first_frame_index == sr[-2].headers[0].frame_index