diff --git a/qurator/dinglehopper/align.py b/qurator/dinglehopper/align.py
index ab44760..87febb7 100644
--- a/qurator/dinglehopper/align.py
+++ b/qurator/dinglehopper/align.py
@@ -28,16 +28,16 @@ def seq_align(s1, s2):
 
         if o:
             if o[0] == 'insert':
-                yield (None, s2[j])
+                yield None, s2[j]
                 j += 1
             elif o[0] == 'delete':
-                yield (s1[i], None)
+                yield s1[i], None
                 i += 1
             elif o[0] == 'replace':
-                yield (s1[i], s2[j])
+                yield s1[i], s2[j]
                 i += 1
                 j += 1
         else:
-            yield (s1[i], s2[j])
+            yield s1[i], s2[j]
             i += 1
             j += 1
diff --git a/qurator/dinglehopper/edit_distance.py b/qurator/dinglehopper/edit_distance.py
index a6643c7..284b676 100644
--- a/qurator/dinglehopper/edit_distance.py
+++ b/qurator/dinglehopper/edit_distance.py
@@ -8,7 +8,6 @@ import numpy as np
 from uniseg.graphemecluster import grapheme_clusters
 
 
-
 def levenshtein_matrix(seq1: Sequence, seq2: Sequence):
     """Compute the matrix commonly computed to produce the Levenshtein distance.
     This is also known as the Wagner-Fischer algorithm. The matrix element at the bottom right contains the desired
diff --git a/qurator/dinglehopper/ocr_files.py b/qurator/dinglehopper/ocr_files.py
index d3918d1..a048b1e 100644
--- a/qurator/dinglehopper/ocr_files.py
+++ b/qurator/dinglehopper/ocr_files.py
@@ -1,5 +1,6 @@
 from __future__ import division, print_function
 
+from typing import Optional
 from warnings import warn
 
 from lxml import etree as ET
@@ -58,21 +59,24 @@ def normalize(text, normalization):
 
 
 # XXX hack
-normalize_sbb = lambda t: normalize(t, Normalization.NFC_SBB)
+def normalize_sbb(t):
+    return normalize(t, Normalization.NFC_SBB)
 
 
 @attr.s(frozen=True)
 class ExtractedTextSegment:
-    segment_id = attr.ib(type=str)
+    segment_id = attr.ib(type=Optional[str])
+
     @segment_id.validator
-    def check(self, attribute, value):
+    def check(self, _, value):
         if value is None:
             return
         if not re.match(r'[\w\d_-]+', value):
             raise ValueError('Malformed segment id "{}"'.format(value))
     text = attr.ib(type=str)
+
     @text.validator
-    def check(self, attribute, value):
+    def check(self, _, value):
         if value is not None and normalize(value, self.normalization) != value:
             raise ValueError('String "{}" is not normalized.'.format(value))
     normalization = attr.ib(converter=Normalization, default=Normalization.NFC_SBB)
diff --git a/qurator/dinglehopper/tests/test_integ_ocrd_cli.py b/qurator/dinglehopper/tests/test_integ_ocrd_cli.py
index 3d78f57..75bb816 100644
--- a/qurator/dinglehopper/tests/test_integ_ocrd_cli.py
+++ b/qurator/dinglehopper/tests/test_integ_ocrd_cli.py
@@ -1,11 +1,9 @@
 import os
-import re
 import shutil
 import json
 from pathlib import Path
 
 from click.testing import CliRunner
-import pytest
 from .util import working_directory
 
 
diff --git a/qurator/dinglehopper/tests/util.py b/qurator/dinglehopper/tests/util.py
index 52b7506..1f224e5 100644
--- a/qurator/dinglehopper/tests/util.py
+++ b/qurator/dinglehopper/tests/util.py
@@ -21,8 +21,8 @@ def diffprint(x, y):
         _diffprint(x, y)
 
 
-def unzip(l):
-    return zip(*l)
+def unzip(an_iterable_of_tuples):
+    return zip(*an_iterable_of_tuples)
 
 
 class working_directory: