如何解决Django项目中的“ImportError:尝试相对导入没有已知的父包”的问题？

myproject/
    manage.py
    myproject/
        __init__.py
        settings.py
        urls.py
        wsgi.py
    myapp/
        __init__.py
        views.py
        models.py

cd myproject
python manage.py runserver

python myproject/myapp/views.py

export PYTHONPATH=/path/to/myproject
python myproject/myapp/views.py

from myproject.myapp.models import MyModel

from .models import MyModel

myproject/
    manage.py
    myproject/
        __init__.py
        settings.py
        urls.py
        wsgi.py
    myapp/
        __init__.py
        views.py
        models.py

from myproject.myapp.models import MyModel