Use a shared executor for all parallel calls

libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py

@@ -171,11 +171,21 @@ async def test_default_method_implementations(mocker: MockerFixture) -> None:
     assert spy.call_args_list == [
         mocker.call(
             "hello",
-            dict(metadata={"key": "value"}, tags=[], callbacks=None, _locals={}),
+            dict(
+                metadata={"key": "value"},
+                tags=[],
+                callbacks=None,
+                _locals={},
+            ),
         ),
         mocker.call(
             "wooorld",
-            dict(metadata={"key": "value"}, tags=[], callbacks=None, _locals={}),
+            dict(
+                metadata={"key": "value"},
+                tags=[],
+                callbacks=None,
+                _locals={},
+            ),
         ),
     ]