code: func (h *Client) CheckoutStepOption(checkoutStepOption string) *Client {
  	h.checkoutStepOption = checkoutStepOption
  	h.checkoutStepOptionSet = true
  	return h
  }
docs: // Additional information about a checkout step. This is an
  // additional parameter that can be sent when Product Action
  // is set to 'checkout'. For analytics.js the Enhanced Ecommerce
  // plugin must be installed before using this field.