[bug] chapter 2 ipynb code

### Enter the chapter number

2

### Enter the page number

can't tell page number because it's on oreilly.com, but it is the section entitled "Create a Test Set"

### What is the cell's number in the notebook

_No response_

### Enter the environment you are using to run the notebook

Jupyter on Windows

### Describe your issue

using jupyter in VS Code, the markdown text that describes the PYTHONHASHSEED environment variable says the variable needs to be set to "0". It really needs to be set to 0. otherwise the initialization of sys hangs.

### Enter what you expected to happen

_No response_

### If you found a workaround, describe it here

set the environment variable to 0