How to use the @covalent/core.StepState.None function in @covalent/core

private doActivate(step: TdStepComponent) {
    // Disable all steps greater than the current step
    const steps = this.stepper.steps;
    const index = steps.indexOf(step);
    const disabled = this.disabledSteps.value;
    for (let i = 0; i < steps.length; i++) {
      const current = steps[i];
      current.disabled = disabled.has(current) || i > index;
      if (i > index) {
        current.state = StepState.None;
      } else if (i < index) {
        if (this.disabledSteps.value.has(current)) {
          current.state = StepState.None;
        } else {
          current.state = StepState.Complete;
        }
      }
    }
    step.state = StepState.None;
    step.open();
  }
}

toggleCompleteStep3(): void {
        this.stateStep3 = (this.stateStep3 === StepState.Complete ? StepState.None : StepState.Complete);
    }

toggleRequiredStep2(): void {
        this.stateStep2 = (this.stateStep2 === StepState.Required ? StepState.None : StepState.Required);
    }