diff --git a/.github/workflows/copilot-setup-steps.yml b/.github/workflows/copilot-setup-steps.yml
new file mode 100644
index 000000000000..a06f3a72fae4
--- /dev/null
+++ b/.github/workflows/copilot-setup-steps.yml
@@ -0,0 +1,32 @@
+name: Copilot Setup Steps
+
+on: workflow_dispatch
+
+jobs:
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.9'
+          cache: 'pip'
+      
+      - name: Create and activate virtual environment
+        run: |
+          python -m venv .venv
+          source .venv/bin/activate
+          echo "VIRTUAL_ENV=$(pwd)/.venv" >> $GITHUB_ENV
+          echo "$(pwd)/.venv/bin" >> $GITHUB_PATH
+      
+      - name: Install Dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -r eng/ci_tools.txt
diff --git a/sdk/translation/azure-ai-translation-document/azure/ai/translation/document/_model_base.py b/sdk/translation/azure-ai-translation-document/azure/ai/translation/document/_model_base.py
index e6a2730f9276..f46cc6a72e4b 100644
--- a/sdk/translation/azure-ai-translation-document/azure/ai/translation/document/_model_base.py
+++ b/sdk/translation/azure-ai-translation-document/azure/ai/translation/document/_model_base.py
@@ -633,7 +633,7 @@ def _deserialize(cls, data, exist_discriminators):
                 discriminator_value = data.find(xml_name).text  # pyright: ignore
         else:
             discriminator_value = data.get(discriminator._rest_name)
-        mapped_cls = cls.__mapping__.get(discriminator_value, cls)  # pyright: ignore
+        mapped_cls = getattr(cls, "__mapping__", {}).get(discriminator_value, cls)
         return mapped_cls._deserialize(data, exist_discriminators)
 
     def as_dict(self, *, exclude_readonly: bool = False) -> typing.Dict[str, typing.Any]: