Minor updates to client_async.py

Author: dpkp

kafka/client_async.py

@@ -5,7 +5,9 @@
 import functools
 import logging
 import random
+import socket
 import threading
+import time
 import weakref
 
 # selectors in stdlib as of py3.4
@@ -15,9 +17,6 @@
     # vendored backport module
     from kafka.vendor import selectors34 as selectors
 
-import socket
-import time
-
 from kafka.vendor import six
 
 from kafka.cluster import ClusterMetadata
@@ -611,7 +610,8 @@ def poll(self, timeout_ms=None, future=None):
         return responses
 
     def _poll(self, timeout):
-        """Returns list of (response, future) tuples"""
+        # This needs to be locked, but since it is only called from within the
+        # locked section of poll(), there is no additional lock acquisition here
         processed = set()
 
         start_select = time.time()