code: func (h *Client) Revenue(revenue float64) *Client {
  	h.revenue = revenue
  	h.revenueSet = true
  	return h
  }
docs: // The total value of the transaction, including tax and shipping.
  // If not sent, this value will be automatically calculated
  // using the product quantity and price fields of all products
  // in the same hit. This is an additional parameter that can
  // be sent when Product Action is set to 'purchase' or 'refund'.
  // For analytics.js the Enhanced Ecommerce plugin must be installed
  // before using this field.