About two ema in Trainer class

[derow0208]

Thanks for your excellent code!
I'm a bit confused about some of the code in the rectified_flow.py file
What's the difference between these two ema model?

            if getattr(self.model, 'use_consistency', False):
                self.model.ema_model.update()

            if self.is_main and self.use_ema:
                self.ema_model.ema_model.data_shape = self.model.data_shape
                self.ema_model.update()

What are their respective functions?