docs(gen_ai): Add Vertex AI Express Mode Sample for Google Gen AI SDK

Author: holtskinner

genai/express_mode/api_key_example.py

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def generate_content() -> str:
+    # [START genai_vertexai_express_mode]
+    from google import genai
+
+    # TODO(developer): Update below line
+    API_KEY = "YOUR_API_KEY"
+
+    client = genai.Client(vertexai=True, api_key=API_KEY)
+
+    response = client.models.generate_content(
+        model="gemini-2.0-flash-exp",
+        contents="""Explain bubble sort to me.""",
+    )
+
+    print(response.text)
+    # Example response:
+    # Bubble Sort is a simple sorting algorithm that repeatedly steps through the list
+    # [END genai_vertexai_express_mode]
+    return response.text

genai/express_mode/api_key_example_test.py

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from unittest.mock import MagicMock, patch
+
+from google.genai import types
+import api_key_example
+
+
+@patch("google.genai.Client")
+def test_api_key_example(mock_genai_client: MagicMock) -> None:
+    # Mock the API response
+    mock_response = types.GenerateContentResponse._from_response(  # pylint: disable=protected-access
+        response={
+            "candidates": [
+                {
+                    "content": {
+                        "parts": [{"text": "This is a mocked bubble sort explanation."}]
+                    }
+                }
+            ]
+        },
+        kwargs={},
+    )
+    mock_genai_client.return_value.models.generate_content.return_value = mock_response
+
+    response = api_key_example.generate_content()
+
+    mock_genai_client.assert_called_once_with(vertexai=True, api_key="YOUR_API_KEY")
+    mock_genai_client.return_value.models.generate_content.assert_called_once_with(
+        model="gemini-2.0-flash-exp",
+        contents="Explain bubble sort to me.",
+    )
+    assert response == "This is a mocked bubble sort explanation."

genai/express_mode/noxfile_config.py

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+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Default TEST_CONFIG_OVERRIDE for python repos.
+
+# You can copy this file into your directory, then it will be imported from
+# the noxfile.py.
+
+# The source of truth:
+# https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/noxfile_config.py
+
+TEST_CONFIG_OVERRIDE = {
+    # You can opt out from the test for specific Python versions.
+    "ignored_versions": ["2.7", "3.7", "3.8", "3.10", "3.11", "3.13"],
+    # Old samples are opted out of enforcing Python type hints
+    # All new samples should feature them
+    "enforce_type_hints": True,
+    # An envvar key for determining the project id to use. Change it
+    # to 'BUILD_SPECIFIC_GCLOUD_PROJECT' if you want to opt in using a
+    # build specific Cloud project. You can also use your own string
+    # to use your own Cloud project.
+    "gcloud_project_env": "GOOGLE_CLOUD_PROJECT",
+    # 'gcloud_project_env': 'BUILD_SPECIFIC_GCLOUD_PROJECT',
+    # If you need to use a specific version of pip,
+    # change pip_version_override to the string representation
+    # of the version number, for example, "20.2.4"
+    "pip_version_override": None,
+    # A dictionary you want to inject into your test. Don't put any
+    # secrets here. These values will override predefined values.
+    "envs": {},
+}

genai/express_mode/requirements-test.txt

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+google-api-core==2.24.0
+pytest==8.2.0

genai/express_mode/requirements.txt

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+google-genai==0.6.0