Fix: Allow None value for parser_config in create_dataset SDK method (#8041)

### What problem does this PR solve?

Fix parser_config=None handling in create_dataset

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

sdk/python/ragflow_sdk/ragflow.py

@@ -57,7 +57,7 @@ class RAGFlow:
         permission: str = "me",
         chunk_method: str = "naive",
         pagerank: int = 0,
-        parser_config: DataSet.ParserConfig = None,
+        parser_config: Optional[DataSet.ParserConfig] = None,
     ) -> DataSet:
         payload = {
             "name": name,
@@ -246,10 +246,7 @@ class RAGFlow:
         raise Exception(res["message"])
 
     def create_agent(self, title: str, dsl: dict, description: str | None = None) -> None:
-        req = {
-            "title": title,
-            "dsl": dsl
-        }
+        req = {"title": title, "dsl": dsl}
 
         if description is not None:
             req["description"] = description
@@ -260,13 +257,7 @@ class RAGFlow:
         if res.get("code") != 0:
             raise Exception(res["message"])
 
-    def update_agent(
-        self,
-        agent_id: str,
-        title: str | None = None,
-        description: str | None = None,
-        dsl: dict | None = None
-    ) -> None:
+    def update_agent(self, agent_id: str, title: str | None = None, description: str | None = None, dsl: dict | None = None) -> None:
         req = {}
 
         if title is not None: