Fixed "model = model = model" typo in tutorial

Description of the change

Typo fix

Choose one: (Bug fix)

[x] I have performed a self-review of my code.
[x] I have added detailed comments to my code where applicable.
[x] I have verified that my change does not break existing code.
[x] My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
[x] I am familiar with the Google Style Guide for the language I have coded in.
[x] I have read through the Contributing Guide and signed the Contributor License Agreement.