def copy(_future):
    if chained.done():
        return
    if (_future.exception() is not None):
        chained.set_exception(_future.exception())
    else:
        chained.set_result(return_value)
def copy(_future):
    if chained.done():
        return
    if (_future.exception() is not None):
        chained.set_exception(_future.exception())
    else:
        chained.set_result(return_value)