Tweeted By @fchollet

Built-in losses and metrics in Keras follow the signature `loss(y_true, y_pred, sample_weight=None)`. If you have exotic losses or metrics, a simple way to add them w/o having to implement your own training loop from scratch is to define them in an "endpoint layer". Like this: pic.twitter.com/UILTVriiuf

— François Chollet (@fchollet) November 25, 2019