DOC: Fixing EX01 - Added examples
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

Towards https://github.com/pandas-dev/pandas/issues/37875

Note: the examples for `pandas.HDFStore.groups` and `pandas.HDFStore.walk` were done [here](https://github.com/pandas-dev/pandas/pull/53889).

Thanks @DeaMariaLeon 