'Constructor.
Args:
service: The service name.
deadline: Optional deadline.  Default depends on the implementation.
callback: Optional argument-less callback function.
stubmap: optional APIProxyStubMap instance, for dependency injection.'

def __init__(self, service, deadline=None, callback=None, stubmap=None):

    if (stubmap is None):
        stubmap = apiproxy
    self.__stubmap = stubmap
    self.__service = service
    self.__rpc = CreateRPC(service, stubmap)
    self.__rpc.deadline = deadline
    self.__rpc.callback = self.__internal_callback
    self.callback = callback
    self.__class__.__local.may_interrupt_wait = False
