keras/src/optimizers/loss_scale_optimizer.py/LossScaleOptimizer/build
class LossScaleOptimizer:    def build(self, var_list):
        self.step_counter = self.add_variable(
            shape=(),
            dtype="int",
            initializer=initializers.Zeros(),
            name="step_counter",
        )
        self.dynamic_scale = self.add_variable(
            shape=(),
            dtype="float32",
            initializer=initializers.Constant(self.initial_scale),
            name="dynamic_scale",
        )
        self.inner_optimizer.build(var_list)
        self.built = True