What is this Android folder icon with a set of three vertical bars in the lower right corner?

问题

Preface

This question is different from What is this Android fodler icon with a small yellow circle in the lower right corner? because I am asking about a different icon. I split these up into their own questions because of this answer to a meta question

Background

I am trying to find the formal name for this folder icon() that appears next to what seems to be helper libraries.

I have looked in the following documentation:

1. The IntelliJ Icon Reference
2. Under Android Studio > Preferences > Editor > File Types (on Mac)

3. Looking at the balloon for the folder when waving the mouse over it:

None of these mention what the folder icon means or if they do they are not specific enough.

Question

What is the name for (

)? Please provide documentation in your answer.

回答1:

This 'Library folder' icon denotes the Project library.

来源：https://stackoverflow.com/questions/52191119/what-is-this-android-folder-icon-with-a-set-of-three-vertical-bars-in-the-lower