diff --git a/src/ansys/dpf/core/collection_base.py b/src/ansys/dpf/core/collection_base.py
index c98cd93cf9..18bc3219ed 100644
--- a/src/ansys/dpf/core/collection_base.py
+++ b/src/ansys/dpf/core/collection_base.py
@@ -424,11 +424,11 @@ def __getitem__(self, index: int | slice):
         """
         if isinstance(index, slice):
             # handle slice
-            indices = list(range(
-                index.start if index.start else 0,
-                index.stop,
-                index.step if index.step else 1
-            ))
+            indices = list(
+                range(
+                    index.start if index.start else 0, index.stop, index.step if index.step else 1
+                )
+            )
             out_collection = self.__class__()
             out_collection.set_labels(labels=self._get_labels())
             if hasattr(out_collection, "add_entry"):
@@ -441,7 +441,7 @@ def __getitem__(self, index: int | slice):
             for i in indices:
                 func(
                     label_space=self.get_label_space(index=i),
-                    entry=self._get_entries(label_space_or_index=i)
+                    entry=self._get_entries(label_space_or_index=i),
                 )
             return out_collection
         self_len = len(self)
diff --git a/tests/test_collection.py b/tests/test_collection.py
index cb73753ca3..017ec3211a 100644
--- a/tests/test_collection.py
+++ b/tests/test_collection.py
@@ -245,14 +245,14 @@ def test_connect_collection_workflow(server_type, subtype_creator):
     assert out is not None
     assert len(out) == 1
 
+
 def test_generic_data_containers_collection_slice(server_type):
     coll = GenericDataContainersCollection(server=server_type)
 
     coll.labels = ["id1", "id2"]
     for i in range(5):
         coll.add_entry(
-            label_space={"id1": i, "id2": 0},
-            entry=create_dummy_gdc(server_type=server_type)
+            label_space={"id1": i, "id2": 0}, entry=create_dummy_gdc(server_type=server_type)
         )
     assert len(coll) == 5
     print(coll)
@@ -268,7 +268,7 @@ def test_string_containers_collection_slice(server_type):
     for i in range(5):
         coll.add_entry(
             label_space={"id1": i, "id2": 0},
-            entry=create_dummy_string_field(server_type=server_type)
+            entry=create_dummy_string_field(server_type=server_type),
         )
     assert len(coll) == 5
     print(coll)