Frappe Asset Bundle Not working

Hi, Frappe asset bundling is not functioning properly, on Frappe website it says that using style.bundle.css and main.bundle.js will enable me to bundle my dependencies, and it will get bundled automatically if bench build is used but every time I use bench build on my custom app it doesn’t pick my style.bundle.css and main.bundle.js.

Am I doing something wrong or is there any extra step I am missing?

Thank you in Advance

Never Mind I found out that I had to install the Develop bench of frappe