Creates an RPC object for use with the Task Queue API.
Optional deadline in seconds for the operation; the default
value is a system-specific deadline, which is typically 5 seconds. After
the deadline, a
DeadlineExceededError error will be returned.
Optional function to be called with the Task Queue service
returns results successfully when
wait() is invoked on the RPC object. The function is
called without arguments. The function is not called in a background
process or thread; the function is only called when one of the above
methods is called by the application. The function is called even if
the request fails or the RPC deadline elapses.