diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e21d7a9..aa4948a 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -21,7 +21,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/python-jsonschema/check-jsonschema
-    rev: 0.27.3
+    rev: 0.27.4
     hooks:
       - id: check-github-workflows
 
@@ -77,7 +77,7 @@ repos:
           ]
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.1.9
+    rev: v0.2.0
     hooks:
       - id: ruff
         types_or: [python, jupyter]
@@ -86,7 +86,7 @@ repos:
         types_or: [python, jupyter]
 
   - repo: https://github.com/scientific-python/cookie
-    rev: "2023.12.21"
+    rev: "2024.01.24"
     hooks:
       - id: sp-repo-review
         additional_dependencies: ["repo-review[cli]"]
diff --git a/jupyterlab_server/licenses_handler.py b/jupyterlab_server/licenses_handler.py
index 27fcac8..c60aaa9 100644
--- a/jupyterlab_server/licenses_handler.py
+++ b/jupyterlab_server/licenses_handler.py
@@ -58,13 +58,11 @@ def federated_extensions(self) -> dict[str, Any]:
 
             assert isinstance(self.parent, LabServerApp)
 
-        labextensions_path: list = sum(
-            [
-                self.parent.labextensions_path,
-                self.parent.extra_labextensions_path,
-            ],
-            [],
-        )
+        per_paths = [
+            self.parent.labextensions_path,
+            self.parent.extra_labextensions_path,
+        ]
+        labextensions_path = [extension for extensions in per_paths for extension in extensions]
         return get_federated_extensions(labextensions_path)
 
     async def report_async(
diff --git a/tests/test_workspaces_api.py b/tests/test_workspaces_api.py
index 9b65855..a1f49c5 100644
--- a/tests/test_workspaces_api.py
+++ b/tests/test_workspaces_api.py
@@ -121,9 +121,10 @@ async def test_listing_dates(jp_fetch, labserverapp):
     r = await jp_fetch("lab", "api", "workspaces")
     data = json.loads(r.body.decode())
     values = data["workspaces"]["values"]
-    times: list = sum(
-        ([ws["metadata"].get("last_modified"), ws["metadata"].get("created")] for ws in values), []
-    )
+    workspaces = [
+        [ws["metadata"].get("last_modified"), ws["metadata"].get("created")] for ws in values
+    ]
+    times = [time for workspace in workspaces for time in workspace]
     assert None not in times
     [rfc3339_to_timestamp(t) for t in times]