尝试从python标准库导入时，出现ImportError。 这仅在使用自定义django管理命令时发生，而在使用常规运行服务器时则不会发生。
这是我得到的错误：
Traceback (most recent call last):
File "D:/stack/sendall/website/sendall/manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "D:\stack\sendall\website\venv\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
utility.execute()
File "D:\stack\sendall\website\venv\lib\site-packages\django\core\management\__init__.py", line 357, in execute
django.setup()
File "D:\stack\sendall\website\venv\lib\site-packages\django\__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "D:\stack\sendall\website\venv\lib\site-packages\django\apps\registry.py", line 112, in populate
app_config.import_models()
File "D:\stack\sendall\website\venv\lib\site-packages\django\apps\config.py", line 198, in import_models
self.models_module = import_module(models_module_name)
File "C:\Users\Joseph\AppData\Local\Programs\Python\Python36-32\lib\importlib\__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 978, in _gcd_import
File "<frozen importlib._bootstrap>", line 961, in _find_and_load
File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 678, in exec_module
File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
File "D:\stack\sendall\website\sendall\accounts\models.py", line 1, in <module>
from typing import AsyncContextManager
ImportError: cannot import name 'AsyncContextManager'
我正在使用python 3.7 希望有人可以帮助我解决这个问题