How to add file attachment button to my Teams bot?

Dear community,

Recently I created a new chatbot application using python and flask framework. It's working good and deployed in Teams as well. Then I planned add file attachment options but unfortunately I couldn't find attachment button in my Teams chatbot!

For R&D purpose I tried below sample codes:

1. https://github.com/microsoft/BotBuilder-Samples/tree/main/samples/python/15.handling-attachments
2. https://github.com/microsoft/BotBuilder-Samples/tree/main/samples/python/56.teams-file-upload

Can anyone guide how to add file attachment button in Teams chatbot app?

Thank you.