Google App Engine:如何以编程方式访问Model类的属性？

import webapp2
from google.appengine.api import api_base_pb2
from google.appengine.ext import ndb

class YourModel(ndb.Model):
    # 自定义属性的设置
    property_name = ndb.StringProperty()

class MyRequestHandler(webapp2.RequestHandler):
    def get(self):
        # 获取模型实例
        model_instance = YourModel.get_by_key_name(self.request.get('key_name'))

        # 定义RPC方法
        rpc_method_name = 'your_rpc_method_%s' % (model_instance.id().split�()[2])
        rpc_method_docstring = 'Get the `%s` attribute of the given model instance.' % rpc_method_name
        rpc_method_response = api_base_pb2.MethodResponse()

        # 实现RPC方法
        def rpc_method(request):
            # 访问模型的属性
            if rpc_method_name.startswith('get__'):
                instance_key = ndb.Key(YourModel, self.kwargs['key_name'])
                instance_value = model_instance.remote_data.get(instance_key)
                rpc_method_response.set_message(rpc_method_docstring % instance_value.property_name)
            elif rpc_method_name.startswith('put__'):
                instance_key = ndb.Key(YourModel, self.kwargs['key_name'])
                instance_data = model_instance.property_name.update(request.get('key'), request.get('value'))
                rpc_method_response.set_message(rpc_method_docstring % instance_data)
            return rpc_method_response
        
        # 记录RPC方法的名称和docstring
        context = {
            'rpc_method_name': rpc_method_name,
            'rpc_method_docstring': rpc_method_docstring,
        }

        # 执行RPC方法
        response = rpc_method(request=context)
        self.response.write(response.SerializeToString())