diff --git a/eva/optimizer/plan_generator.py b/eva/optimizer/plan_generator.py
index e761620493..6328097950 100644
--- a/eva/optimizer/plan_generator.py
+++ b/eva/optimizer/plan_generator.py
@@ -115,7 +115,9 @@ def _recursive_strip_exchange(plan: AbstractPlan, is_top: bool = False):
                     plan.append_child(child)
 
                 if isinstance(plan, ExchangePlan):
-                    assert not is_top or len(plan.children) == 1, "Top ExchangePlan can only have 1 child."
+                    assert (
+                        not is_top or len(plan.children) == 1
+                    ), "Top ExchangePlan can only have 1 child."
                     return plan.children
                 else:
                     return [plan]
diff --git a/test/integration_tests/test_like.py b/test/integration_tests/test_like.py
index cb2d17cab9..6d3b9049bc 100644
--- a/test/integration_tests/test_like.py
+++ b/test/integration_tests/test_like.py
@@ -13,11 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import unittest
+from test.util import shutdown_ray
 
 from eva.catalog.catalog_manager import CatalogManager
 from eva.configuration.constants import EVA_ROOT_DIR
 from eva.server.command_handler import execute_query_fetch_all
-from test.util import shutdown_ray
 
 
 class LikeTest(unittest.TestCase):
diff --git a/test/optimizer/test_cascade_optimizer.py b/test/optimizer/test_cascade_optimizer.py
index e7fcad4097..67a51c1f55 100644
--- a/test/optimizer/test_cascade_optimizer.py
+++ b/test/optimizer/test_cascade_optimizer.py
@@ -19,13 +19,13 @@
 import pytest
 
 from eva.catalog.catalog_manager import CatalogManager
+from eva.experimental.ray.planner.exchange_plan import ExchangePlan
 from eva.models.storage.batch import Batch
-from eva.server.command_handler import execute_query_fetch_all
-from eva.plan_nodes.project_plan import ProjectPlan
+from eva.optimizer.plan_generator import PlanGenerator
 from eva.plan_nodes.nested_loop_join_plan import NestedLoopJoinPlan
+from eva.plan_nodes.project_plan import ProjectPlan
 from eva.plan_nodes.storage_plan import StoragePlan
-from eva.experimental.ray.planner.exchange_plan import ExchangePlan
-from eva.optimizer.plan_generator import PlanGenerator
+from eva.server.command_handler import execute_query_fetch_all
 
 
 @pytest.mark.notparallel