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

        Args:
            var_list: list of model variables to build Ftrl variables on.
        """
        if self.built:
            return
        super().build(var_list)
        accumulator_initializer = initializers.Constant(
            self.initial_accumulator_value,
        )
        self._accumulators, self._linears = self.add_optimizer_variables(
            var_list,
            ["accumulator", "linear"],
            initializer=[accumulator_initializer, "zeros"],
        )
Initialize optimizer variables.

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