def taxes_for_shipment(shipment_key)
      shipment = shipment_sales_tax_rates.select { |s| s[:@shipment_key] == shipment_key }.first

      # convert attribute keys to symbols
      freight = attributes_to_symbols(shipment[:freight_sales_tax_rate])

      # wrap products in ProductSalesTaxRate
      products = wrap_products(shipment[:product_sales_tax_rates])

      ShipmentSalesTaxRate.new(shipment_key, FreightSalesTaxRate.new(freight), products)
    end
def taxes_for_shipment(shipment_key)
      shipment = shipment_sales_tax_rates.select { |s| s[:@shipment_key] == shipment_key }.first

      # convert attribute keys to symbols
      freight = attributes_to_symbols(shipment[:freight_sales_tax_rate])

      # wrap products in ProductSalesTaxRate
      products = wrap_products(shipment[:product_sales_tax_rates])

      ShipmentSalesTaxRate.new(shipment_key, FreightSalesTaxRate.new(freight), products)
    end
Access the tax information for a shipment. Returns an instance of
 ShipmentSalesTaxRate.