keras/src/backend/tensorflow/optimizer.py/TFOptimizer/_clip_by_norm
class TFOptimizer:    def _clip_by_norm(self, values, axes=None):
        # We need to use TF-specific OP to support the case,
        # when `values` are `tf.IndexedSlices`.
        return tf.clip_by_norm(values, self.clipnorm, axes)