'Decorator which enters \'sync:\' mode to the selected transport,
then invokes the decorated funciton.'

def _sync(fn):

    @functools.wraps(fn)
    def wrapper(self, *a, **kw):
        rv = None
        if (FAIL != self.send('sync:')):
            rv = fn(self, *a, **kw)
        return rv
    return wrapper
