fix ruff linting issues and sort imports in thread-safety tests

Author: Deadpool2000

openapi_python_sdk/oauth_client.py

@@ -35,7 +35,6 @@ def client(self) -> Any:
         """
         if self._client is not None:
             return self._client
-
         if not hasattr(self._thread_local, "client"):
             self._thread_local.client = httpx.Client(timeout=self.timeout)
         return self._thread_local.client

tests/test_thread_safety.py

@@ -1,8 +1,11 @@
 import threading
 import unittest
-from openapi_python_sdk import Client, OauthClient
+
 import httpx
 
+from openapi_python_sdk import Client, OauthClient
+
+
 class TestThreadSafety(unittest.TestCase):
     def test_oauth_client_thread_safety(self):
         oauth = OauthClient(username="user", apikey="key")