[Python] Avoid pep8 violation (#4316)

samples/client/petstore/python-asyncio/petstore_api/api_client.py

@@ -11,6 +11,7 @@
 from __future__ import absolute_import
 
 import datetime
+from dateutil.parser import parse
 import json
 import mimetypes
 from multiprocessing.pool import ThreadPool
@@ -578,7 +579,6 @@ class ApiClient(object):
         :return: date.
         """
         try:
-            from dateutil.parser import parse
             return parse(string).date()
         except ImportError:
             return string
@@ -597,7 +597,6 @@ class ApiClient(object):
         :return: datetime.
         """
         try:
-            from dateutil.parser import parse
             return parse(string)
         except ImportError:
             return string