fix linting errors

lightrag/kg/tidb_impl.py

@@ -5,17 +5,19 @@ from typing import Union
 
 import numpy as np
 import pipmaster as pm
+
 if not pm.is_installed("pymysql"):
     pm.install("pymysql")
 if not pm.is_installed("sqlalchemy"):
     pm.install("sqlalchemy")
-    
+
 from sqlalchemy import create_engine, text
 from tqdm import tqdm
 
 from lightrag.base import BaseVectorStorage, BaseKVStorage, BaseGraphStorage
 from lightrag.utils import logger
 
+
 class TiDB(object):
     def __init__(self, config, **kwargs):
         self.host = config.get("host", None)