Deploy a local modification of Node module to firebase functions

I am developing some firebase functions, and one in particular does not work to an issue in one of the node modules on which my function depend.

I already found where is the issue and how to fix it, the problem is that, if I modify the source in node_modules/ folder, that update is not sent to the server. I removed from the package.json the dependency and did (before modify the file locally):

npm install --save pdf2img

But the function is not updated, the error is always the same. Is it possibile to do what I would or not?

Thanks for anyone providing help!

via N Dorigatti