No files under site.collections

Hi, I am trying to create a collection and iterate over it to list all my files but when I print site.collections
it shows nothing under files:

[{“label”:“Binary_Systems”,“files”:[],“output”:true,“docs”:[],“directory”:"/home/igaurab/Documents/Github/Book/_Binary_Systems",“relative_directory”:"_Binary_Systems"},{“label”:“Boolean_Algebra”,“files”:[],“output”:true,“docs”:

Although I haves 4 files within the Binary_systems folder.
This is my config:

collections_dir: book
collections:
Binary_Systems:
output: true
Boolean_Algebra:
output: true

any formatting you may have is stripped when you post code without using backticks to mark it as code. There is also the </> code button in the editor to mark stuff as code.

Do you have a link to the repo?

I think collections are supposed to start with an underscore in the file system.