diff --git a/saqc/funcs/drift.py b/saqc/funcs/drift.py
index e0e58156092cc71d00cf3603c3f85c183dc6fd8f..5f2798b72d4a91d31b0555e6e13d6367c0adbf6c 100644
--- a/saqc/funcs/drift.py
+++ b/saqc/funcs/drift.py
@@ -24,9 +24,9 @@ from saqc.core import DictOfSeries, Flags, flagging, register
 from saqc.funcs.changepoints import _getChangePoints
 from saqc.lib.checking import (
     validateCallable,
+    validateFrequency,
     validateValueBounds,
     validateWindow,
-    validateFrequency,
 )
 from saqc.lib.docs import DOC_TEMPLATES
 from saqc.lib.tools import detectDeviants, filterKwargs, toSequence
@@ -148,7 +148,7 @@ class DriftMixin:
             )
             window = kwargs["freq"]
 
-        validateFrequency(window, 'window')
+        validateFrequency(window, "window")
         fields = toSequence(field)
 
         data = self._data[fields].to_pandas()
diff --git a/saqc/lib/checking.py b/saqc/lib/checking.py
index b26dae1d04750f00438db8ffd9649e641bc841bf..20623305d8cc1ef8cffbfbb6d6469499b834d8c5 100644
--- a/saqc/lib/checking.py
+++ b/saqc/lib/checking.py
@@ -213,10 +213,10 @@ def validateValueBounds(
 
 
 def validateFrequency(
-        value: str | pd.offsets.BaseOffset | pd.Timedelta,
-        name: str,
-        allow_str: bool = True,
-        fixed_only=False
+    value: str | pd.offsets.BaseOffset | pd.Timedelta,
+    name: str,
+    allow_str: bool = True,
+    fixed_only=False,
 ):
     # we might want to use checking.py in tools.py, so we use a
     # late import here, to avoid circular import errors
diff --git a/saqc/lib/tools.py b/saqc/lib/tools.py
index dbdffd3c8036e533115b40dbf9b4ed2922b89343..cd515cff7e833c9911b1fac4c651efa10e300b5e 100644
--- a/saqc/lib/tools.py
+++ b/saqc/lib/tools.py
@@ -17,13 +17,13 @@ from typing import (
     Any,
     Callable,
     Collection,
+    Iterable,
     List,
     Literal,
     Sequence,
     Tuple,
     TypeVar,
     Union,
-    Iterable,
 )
 
 import numpy as np