keras/src/optimizers/adamax.py/Adamax/build
class Adamax:    def build(self, var_list):
        """Initialize optimizer variables.

        Adamax optimizer has 2 types of variables: momentums (denoted as m),
        exponentially weighted infinity norm (denoted as u).

        Args:
            var_list: list of model variables to build Adamax variables on.
        """
        if self.built:
            return
        super().build(var_list)
        self._m = []
        self._u = []
        for var in var_list:
            self._m.append(
                self.add_variable_from_reference(
                    reference_variable=var, name="momentum"
                )
            )
            self._u.append(
                self.add_variable_from_reference(
                    reference_variable=var, name="norm"
                )
            )