If it helps here is a bit more context. The goal here is to keep the signal bullishg_rolling signal high after we get the first bullish_now signal and until bullish_stop is triggered.
self.bullish = bt.And(super_fast > fast, fast > slow, self.data_low > super_fast)
self.bullish_now = bt.And(1 - self.bullish(-1), self.bullish)
self.bullish_stop = super_fast <= fast
super_fast,fast,slow are EMAs