def find_shipment(shipment_key)
      shipment = shipments.select { |s| s[:shipment_key] == shipment_key }.first
      Shipment.new(shipment)
    end
def find_shipment(shipment_key)
      shipment = shipments.select { |s| s[:shipment_key] == shipment_key }.first
      Shipment.new(shipment)
    end
Finds a shipment by +ShipmentKey+. Returns an instance of ShipCompliant::Shipment.

   shipment = sales_order.find_shipment('1')
   puts shipment.ship_date #=> DateTime