Add mypy to CI

Author: suaaa7

.github/workflows/test_for_python_test_example.yml

@@ -15,8 +15,11 @@ jobs:
     - name: Install Library
       run: |
         python3 -m pip install --upgrade pip
-        pip install requests flask
+        pip install requests flask mypy
     - name: Run unittest
       run: |
         cd python_test_example
         python3 -m unittest discover --verbose --pattern "*_test.py"
+    - name: Run mypy
+      run: |
+        mypy .