chore: import upstream snapshot with attribution

contributing/samples/adk_team/adk_knowledge_agent/agent.py

@@ -0,0 +1,73 @@
+# Copyright 2026 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.
+
+import json
+from typing import Optional
+
+from google.adk.agents import LlmAgent
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.models import LlmResponse
+from google.adk.tools.vertex_ai_search_tool import VertexAiSearchTool
+from google.genai import types
+
+VERTEXAI_DATASTORE_ID = "projects/adk-agent-builder-assistant/locations/global/collections/default_collection/dataStores/adk-agent-builder-sample-datastore_1758230446136"
+
+
+def citation_retrieval_after_model_callback(
+    callback_context: CallbackContext,
+    llm_response: LlmResponse,
+) -> Optional[LlmResponse]:
+  """Callback function to retrieve citations after model response is generated."""
+  grounding_metadata = llm_response.grounding_metadata
+  if not grounding_metadata:
+    return None
+
+  content = llm_response.content
+  if not llm_response.content:
+    return None
+
+  parts = content.parts
+  if not parts:
+    return None
+
+  # Add citations to the response as JSON objects.
+  parts.append(types.Part(text="References:\n"))
+  for grounding_chunk in grounding_metadata.grounding_chunks:
+    retrieved_context = grounding_chunk.retrieved_context
+    if not retrieved_context:
+      continue
+
+    citation = {
+        "title": retrieved_context.title,
+        "uri": retrieved_context.uri,
+        "snippet": retrieved_context.text,
+    }
+    parts.append(types.Part(text=json.dumps(citation)))
+
+  return LlmResponse(content=types.Content(parts=parts))
+
+
+root_agent = LlmAgent(
+    name="adk_knowledge_agent",
+    description=(
+        "Agent for performing Vertex AI Search to find ADK knowledge and"
+        " documentation"
+    ),
+    instruction="""You are a specialized search agent for an ADK knowledge base.
+
+      You can use the VertexAiSearchTool to search for ADK examples and documentation in the document store.
+      """,
+    tools=[VertexAiSearchTool(data_store_id=VERTEXAI_DATASTORE_ID)],
+    after_model_callback=citation_retrieval_after_model_callback,
+)