Are you running the lab locally or in the browser environment? If you’re running it locally, make sure that the helper .py file containing load_data() is accessible to your code. If you’re in the browser lab, try restarting the kernel and running all cells again to make sure everything is properly loaded (or maybe reload the lab files).
Hope it helps! Feel free to ask if you need further assistance.
Every time you open a notebook file, you must run all of the cells starting from the top. That is where the assets are imported, and the workspace is created.