diff --git a/cirq-core/cirq/ops/op_tree.py b/cirq-core/cirq/ops/op_tree.py
index 0bbe64e2167..56ba6af4073 100644
--- a/cirq-core/cirq/ops/op_tree.py
+++ b/cirq-core/cirq/ops/op_tree.py
@@ -12,8 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""A recursive type describing trees of operations, and utility methods for it.
-"""
+"""A recursive type describing trees of operations, and utility methods for it."""
 
 from typing import Callable, Iterable, Iterator, NoReturn, Union, TYPE_CHECKING
 
diff --git a/cirq-core/cirq/transformers/dynamical_decoupling.py b/cirq-core/cirq/transformers/dynamical_decoupling.py
index 0a8f6365bbf..804056a8e59 100644
--- a/cirq-core/cirq/transformers/dynamical_decoupling.py
+++ b/cirq-core/cirq/transformers/dynamical_decoupling.py
@@ -83,7 +83,7 @@ def _validate_dd_sequence(dd_sequence: Tuple[ops.Gate, ...]) -> None:
 
 
 def _parse_dd_sequence(
-    schema: Union[str, Tuple[ops.Gate, ...]]
+    schema: Union[str, Tuple[ops.Gate, ...]],
 ) -> Tuple[Tuple[ops.Gate, ...], Dict[ops.Gate, ops.Pauli]]:
     """Parses and returns dynamical decoupling sequence and its associated pauli map from schema."""
     dd_sequence = None