[HANDS-ON BUG]

# Describe the bug

In unit2.ipynb in the first code cell, `pickle5` pip install fails. `pickle5` is only needed in Python versions older than 3.8. Perhaps include a version check before installing?

**Please share your notebook link so that we can reproduce the error**
https://github.com/mksachs/DRLC/blob/main/notebooks/unit2/unit2.ipynb

# Material

- Did you use Google Colab? yes

If not:
- Your Operating system (OS)
- Version of your OS

Open notebooks/unit2/unit2.ipynb and inspect the first code cell. Run it in Google Colab with the available Python version, then verify that the pickle5 installation is only attempted when needed. Done means the first cell runs successfully on supported Python versions, including older versions that require pickle5.

Written by the indexing model from the issue text.