安装ttkbootstrap，提示失败
AttributeError: module 'ttkbootstrap' has no attribute 'Window'
ttkbootstrap我也安装了，但是还是提示报错，引包错误。
C:\Users\silve>pip install ttkbootstrap
Requirement already satisfied: ttkbootstrap in c:\python36\lib\site-packages (0.5.3)
Requirement already satisfied: pillow>=8.2.0 in c:\python36\lib\site-packages (from ttkbootstrap) (8.4.0)
也按照网上的说法，加入指定目录，可是我的安装路径就是这个路径啊，其他pip的包都没有问题。请问大家，这是咋回事啊！！
C:\Users\silve>pip install --target=c:\python36\lib\site-packages ttkbootstrap
Collecting ttkbootstrap
Using cached ttkbootstrap-0.5.3-py3-none-any.whl (47 kB)
Collecting pillow>=8.2.0
Using cached Pillow-8.4.0-cp36-cp36m-win_amd64.whl (3.2 MB)
Installing collected packages: pillow, ttkbootstrap
Successfully installed pillow-8.4.0 ttkbootstrap-0.5.3
WARNING: Target directory c:\python36\lib\site-packages\PIL already exists. Specify --upgrade to force replacement.
WARNING: Target directory c:\python36\lib\site-packages\Pillow-8.4.0.dist-info already exists. Specify --upgrade to force replacement.
WARNING: Target directory c:\python36\lib\site-packages\ttkbootstrap already exists. Specify --upgrade to force replacement.
WARNING: Target directory c:\python36\lib\site-packages\ttkbootstrap-0.5.3.dist-info already exists. Specify --upgrade to force replacement.
WARNING: Target directory c:\python36\lib\site-packages\ttkcreator already exists. Specify --upgrade to force replacement.
