Fixing the documentation for the put<S>(...) method

This PR is fixing the documentation for the ```put<S>(...)``` method which seems to have been corrupted at some point. Adding a small note as well to say that if the instance already exists, this just works like the find method. ## Pre-launch Checklist - [X] I updated/added relevant documentation (doc comments with `///`). - [X] I added new tests to check the change I am making or feature I am adding, or @jonataslaw said the PR is test-exempt. - [X] All existing and new tests are passing.