chore: format and lint fixes for DiffChannel implementation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py

@@ -469,7 +469,9 @@ class PostgresSaver(BasePostgresSaver):
                     break
 
             payloads.reverse()
-            result[channel] = DiffChainValue(base=base, deltas=[p["d"] for p in payloads])
+            result[channel] = DiffChainValue(
+                base=base, deltas=[p["d"] for p in payloads]
+            )
         return result
 
     def _load_checkpoint_tuple(self, value: DictRow) -> CheckpointTuple:

libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

@@ -430,7 +430,9 @@ class AsyncPostgresSaver(BasePostgresSaver):
                     break
 
             payloads.reverse()
-            result[channel] = DiffChainValue(base=base, deltas=[p["d"] for p in payloads])
+            result[channel] = DiffChainValue(
+                base=base, deltas=[p["d"] for p in payloads]
+            )
         return result
 
     async def _load_checkpoint_tuple(self, value: DictRow) -> CheckpointTuple:

libs/checkpoint-postgres/langgraph/checkpoint/postgres/base.py

@@ -208,7 +208,9 @@ class BasePostgresSaver(BaseCheckpointSaver[str]):
 
         if diff_channel_payloads:
             result.update(
-                self._load_diff_chains(thread_id, checkpoint_ns, diff_channel_payloads, cur=cur)
+                self._load_diff_chains(
+                    thread_id, checkpoint_ns, diff_channel_payloads, cur=cur
+                )
             )
 
         return result