Used as a callback to keep the result from the previous callback
    and use that instead of the result of the given callback when
    chaining to the next callback in the fiber.

def bridge_param(_param, _method, *args, **kwargs):
    """
    Used as a callback to keep the result from the previous callback
    and use that instead of the result of the given callback when
    chaining to the next callback in the fiber.
    """
    assert callable(_method), "method %r is not callable" % (_method, )
    f = Fiber(debug_depth=1, debug_call=_method)
    f.add_callback(drop_param, _method, *args, **kwargs)
    f.add_callback(override_result, _param)
    return f.succeed()