The Data Attribute Recommendation - Security Guide

Good day!

Please explain the text in the Security Guide section:
"Never copy and paste your service key into your Python code.
Avoid committing your key to public source code hosting such as GitHub. "

Read this text as:

- the user can randomly put the Python code with a service key in the GitHub
or
- does it mean that the code can be automatically published in open sources?

Thanks!