ModuleNotFoundError: No module named '_contextvars'

Traceback (most recent call last):

  File "D:/MNIST_Demo/main.py", line 3, in <module>

    from flask import Flask, jsonify, render_template, request

  File "D:\MNIST_Demo\venv_one\lib\site-packages\flask\__init__.py", line 14, in <module>

    from jinja2 import escape

  File "D:\MNIST_Demo\venv_one\lib\site-packages\jinja2\__init__.py", line 82, in <module>

    _patch_async()

  File "D:\MNIST_Demo\venv_one\lib\site-packages\jinja2\__init__.py", line 78, in _patch_async

    from jinja2.asyncsupport import patch_all

  File "D:\MNIST_Demo\venv_one\lib\site-packages\jinja2\asyncsupport.py", line 13, in <module>

    import asyncio

  File "D:\Python\Anaconda\lib\asyncio\__init__.py", line 8, in <module>

    from .base_events import *

  File "D:\Python\Anaconda\lib\asyncio\base_events.py", line 39, in <module>

    from . import events

  File "D:\Python\Anaconda\lib\asyncio\events.py", line 14, in <module>

    import contextvars

  File "D:\Python\Anaconda\lib\contextvars.py", line 1, in <module>

    from _contextvars import Context, ContextVar, Token, copy_context

ModuleNotFoundError: No module named '_contextvars'

求大佬解答