def build(self, var_list):
        """Initialize optimizer variables.

        Lion optimizer has one variable `momentums`.

        Args:
            var_list: list of model variables to build Lion variables on.
        """
        if self.built:
            return
        super().build(var_list)
        self._momentums = self.add_optimizer_variables(var_list, "momentum")
Initialize optimizer variables.

        Lion optimizer has one variable `momentums`.

        Args:
            var_list: list of model variables to build Lion variables on.
        
keras/src/optimizers/lion.py