keras/src/backend/tensorflow/optimizer.py/TFOptimizer/stateless_apply
class TFOptimizer:    def stateless_apply(self, optimizer_variables, grads, trainable_variables):
        # This is mainly due to the interaction with tf.distribute.Strategy,
        # which requires tf.Variable as the inputs for most of its APIs.
        raise ValueError(
            "stateless_apply is not supported with the TensorFlow backend "
            "(as it is incompatible with tf.distribute)."
        )