'Waits on the API call associated with this RPC. The callback,
if provided, will be executed before Wait() returns. If this RPC
is already complete, or if the RPC was never started, this
function will return immediately.
Raises:
InterruptedError if a callback throws an uncaught exception.'

def _WaitImpl(self):

    try:
        rpc_completed = _apphosting_runtime___python__apiproxy.Wait(self)
    except (runtime.DeadlineExceededError, apiproxy_errors.InterruptedError):
        raise
    except:
        (exc_class, exc, tb) = sys.exc_info()
        if (isinstance(exc, SystemError) and (exc.args[0] == 'uncaught    RPC    exception')):
            raise
        rpc = None
        if hasattr(exc, '_appengine_apiproxy_rpc'):
            rpc = exc._appengine_apiproxy_rpc
        new_exc = apiproxy_errors.InterruptedError(exc, rpc)
        raise new_exc.__class__, new_exc, tb
    return True
