为什么会显示json没有属性dumps

# coding:utf-8

import json


def write(path, data):
   with open(path, 'w', encoding='utf-8') as f:
       if isinstance(data, dict):
           _data = json.dumps(data)
           f.write(_data)
       else:
           raise TypeError('data is dict')
   return True

data = {'name':'nihao', 'age':18}


if __name__ == '__main__':
   write('test.json', data)