code: func (h *Client) ProductQuantity(productQuantity int64) *Client {
  	h.productQuantity = productQuantity
  	h.productQuantitySet = true
  	return h
  }
docs: // The quantity of a product. Product index must be a positive
  // integer between 1 and 200, inclusive. For analytics.js the
  // Enhanced Ecommerce plugin must be installed before using
  // this field.