What is the privacy term of using a third-party package to access user data?

It may seem like I'm too worried and crazy about privacy, but I'm still curious.

I am developing an application using Flutter and Dart, developed by Google. And I'll need to access the image of the user, so I use the image_picker package. I am curious to know what is the term of confidentiality concerning this. Will Google also get the images when users download them in my app?
In general, I wonder what is the duration of confidentiality of using a third-party package to access user data?