What is this Android folder icon with a set of thr

Question

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.

Answer 1

This 'Library folder' icon denotes the Project library.