add 3.9 compliance tests

Author: chelsea-lin

.github/workflows/unittest.yml

@@ -62,7 +62,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: ['3.12']
+        python: ['3.9', '3.10', '3.11', '3.12']
     steps:
     - name: Checkout
       uses: actions/checkout@v4