Specify thread-safety of grpc-created channels

src/python/grpcio/grpc/__init__.py

@@ -1572,13 +1572,15 @@ def channel_ready_future(channel):
 def insecure_channel(target, options=None):
     """Creates an insecure Channel to a server.
 
+    The returned Channel is thread-safe.
+
     Args:
       target: The server address
       options: An optional list of key-value pairs (channel args
         in gRPC Core runtime) to configure the channel.
 
     Returns:
-      A Channel object.
+      A Channel.
     """
     from grpc import _channel  # pylint: disable=cyclic-import
     return _channel.Channel(target, () if options is None else options, None)
@@ -1587,6 +1589,8 @@ def insecure_channel(target, options=None):
 def secure_channel(target, credentials, options=None):
     """Creates a secure Channel to a server.
 
+    The returned Channel is thread-safe.
+
     Args:
       target: The server address.
       credentials: A ChannelCredentials instance.
@@ -1594,7 +1598,7 @@ def secure_channel(target, credentials, options=None):
         in gRPC Core runtime) to configure the channel.
 
     Returns:
-      A Channel object.
+      A Channel.
     """
     from grpc import _channel  # pylint: disable=cyclic-import
     return _channel.Channel(target, () if options is None else options,