Is there any way to delete useless functions in JS libraries?

I’m building a project in javascript, using paper.js in some features.
Most of my project is built in vanilla Javascript, just some minimum but important features are built with paper.js

The problem is that the library (.min library) is 200kb.
The normal library is 300kb, I was wondering if there is an automatic way to see which functions are being used in the main paper.js library, in order to delete the useless functions.
If there is no program or automatic way to do this, maybe some advice of how to do it manually, or which tools you recommend for me and my team in order to delete useless functions, then minify the file and run it smaller.

Thank you all guys, I did not added any specific code because I want this anwser to be global.

Greetings