Fix for Notebook Error When Re-running Code Without Reloading Data

Raja A. There was a bit of an issue in the notebook where, if the line you ran, is re-run twice, without reloading prod_df you will get an error. You can either re-run the notebook from scratch or the team put a small fix in here so that problem doesn't happen. https://colab.research.google.com/drive/1JtdwykTXPzOI-XNmQ-xEwCBaFhlMVbUk?usp=sharing