title: Add API code examples for remaining main classes
comments: The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_4292). All of your documentation changes will be reflected on that endpoint.
body: This PR adds API code examples for the remaining functions in the Main classes. I wasn't too familiar with some of the functions (`decode_batch`, `decode_column`, `decode_example`, etc.) so please feel free to add an example of usage and I can fill in the rest :)