address comments.

Author: tvalentyn

sdks/python/apache_beam/runners/worker/channel_factory.py

@@ -23,10 +23,10 @@
 
 class GRPCChannelFactory(grpc.StreamStreamClientInterceptor):
   DEFAULT_OPTIONS = [
-      # keep 20 seconds for now. This is needed for other options to work.
-      ("grpc.keepalive_time_ms", 20000),
-      # keep 5 minutes for now.
-      ("grpc.keepalive_timeout_ms", 300000),
+      # Setting keepalive_time_ms is needed for other options to work.
+      ("grpc.keepalive_time_ms", 20_000),
+      # Default: 20s. Increasing to 5 min.
+      ("grpc.keepalive_timeout_ms", 300_000),
       # Default: 2, set to 0 to allow unlimited pings without data
       ("grpc.http2.max_pings_without_data", 0),
       # Default: False, set to True to allow keepalive pings when no calls