On import: ImportError: cannot import name 'gcd' from 'fractions' (/usr/lib/python3.10/fractions.py)

On `import dolo` getting error:

```
ImportError: cannot import name 'gcd' from 'fractions' (/usr/lib/python3.10/fractions.py)
```

This appears to be due to a deprecated Python feature, removed in Python 3.9, which is still in `quantecon`:

https://stackoverflow.com/questions/66174862/import-error-cant-import-name-gcd-from-fractions

I don't see a Python version limit in the docs.