Add experimental option to run unary-stream RPCs on a single Python thread.

src/python/grpcio/grpc/__init__.py

@@ -1953,6 +1953,17 @@ class Compression(enum.IntEnum):
     Gzip = _compression.Gzip
 
 
+class ChannelOptions(object):
+    """Indicates a channel option unique to gRPC Python.
+
+     This enumeration is part of an EXPERIMENTAL API.
+
+     Attributes:
+       SingleThreadedUnaryStream: Perform unary-stream RPCs on a single thread.
+  """
+    SingleThreadedUnaryStream = "SingleThreadedUnaryStream"
+
+
 ###################################  __all__  #################################
 
 __all__ = (