keras/src/constraints/constraints.py/MaxNorm/__call__
class MaxNorm:    def __call__(self, w):
        w = backend.convert_to_tensor(w)
        norms = ops.sqrt(ops.sum(ops.square(w), axis=self.axis, keepdims=True))
        desired = ops.clip(norms, 0, self.max_value)
        return w * (desired / (backend.epsilon() + norms))