用restful api设计并实现shipping and transportation服务，给我一段代码

这里提供一个简单的示例代码，实现了一个基于RESTful API的货物运输服务。

from flask import Flask, jsonify, request

app = Flask(__name__)

# Mock database for demonstration purposes
shipments = [
    {"id": 1, "name": "Shipment 1", "origin": "New York", "destination": "Los Angeles"},
    {"id": 2, "name": "Shipment 2", "origin": "Chicago", "destination": "Boston"}
]

# Get all shipments
@app.route('/shipments', methods=['GET'])
def get_shipments():
    return jsonify(shipments)

# Get a shipment by ID
@app.route('/shipments/<int:id>', methods=['GET'])
def get_shipment(id):
    shipment = next((shipment for shipment in shipments if shipment["id"] == id), None)
    if shipment:
        return jsonify(shipment)
    else:
        return jsonify({"error": "Shipment not found"}), 404

# Create a new shipment
@app.route('/shipments', methods=['POST'])
def create_shipment():
    shipment = request.get_json()
    shipment["id"] = max(shipments, key=lambda x:x["id"])["id"] + 1 # auto-increment ID
    shipments.append(shipment)
    return jsonify(shipment)

# Update a shipment by ID
@app.route('/shipments/<int:id>', methods=['PUT'])
def update_shipment(id):
    shipment = next((shipment for shipment in shipments if shipment["id"] == id), None)
    if shipment:
        updated_shipment = request.get_json()
        shipment.update(updated_shipment)
        return jsonify(shipment)
    else:
        return jsonify({"error": "Shipment not found"}), 404

# Delete a shipment by ID
@app.route('/shipments/<int:id>', methods=['DELETE'])
def delete_shipment(id):
    shipment = next((shipment for shipment in shipments if shipment["id"] == id), None)
    if shipment:
        shipments.remove(shipment)
        return jsonify({"message": "Shipment deleted"})
    else:
        return jsonify({"error": "Shipment not found"}), 404

if __name__ == '__main__':
    app.run(debug=True)

这个示例代码使用了Python的Flask框架，定义了五个不同的路由，分别对应获取所有货运、按ID获取单个货运、创建新货运、更新现有货运和删除现有货运。每个路由都提供了RESTful API所需的HTTP方法，并使用JSON格式作为数据传输格式。