python单元测试在模拟pytz获取本地时间时出现问题

import unittest
from unittest import mock
import pytz

def get_local_time():
    local_tz = pytz.timezone('Asia/Shanghai')
    return pytz.datetime.datetime.now(local_tz)

class MyTestCase(unittest.TestCase):
    def test_get_local_time(self):
        # 模拟pytz获取本地时间的行为
        with mock.patch('pytz.datetime.datetime') as mock_datetime:
            # 设置模拟的本地时间
            mock_datetime.now.return_value = pytz.datetime.datetime(2022, 1, 1, 12, 0, 0)
            
            # 调用要测试的函数
            result = get_local_time()
            
            # 断言结果是否符合预期
            self.assertEqual(result, pytz.datetime.datetime(2022, 1, 1, 12, 0, 0))

if __name__ == '__main__':
    unittest.main()