chore: add GitHub Actions check to run mypy

PiperOrigin-RevId: 737701291

Author: sararob

.github/workflows/mypy.yml

@@ -0,0 +1,32 @@
+# This workflow runs mypy for static type checking.
+# See https://mypy.readthedocs.io/en/stable/index.html for more information.
+#
+# You can adjust the behavior by modifying this file.
+name: Run mypy
+
+on:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.9'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install mypy
+          pip install -r requirements.txt
+
+      - name: Run mypy
+        run: mypy google/genai/ --config-file=google/genai/mypy.ini

google/genai/mypy.ini

@@ -0,0 +1,5 @@
+[mypy]
+exclude = tests/.*
+plugins = pydantic.mypy
+; these are environment-specific imports
+disable_error_code = import-not-found, import-untyped