Format the generator test's sink helper

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/tests/flow/test_workers.py

@@ -38,7 +38,11 @@ def _sink_node(node_id: str, port: str, dtype: DType) -> tuple[Node, list[dict]]
     node._pipeline = type(
         "Recorder",
         (),
-        {"publish_emission": staticmethod(lambda _node, outputs: published.append(outputs))},
+        {
+            "publish_emission": staticmethod(
+                lambda _node, outputs: published.append(outputs)
+            )
+        },
     )()
     return node, published