chore: import upstream snapshot with attribution

contributing/samples/context_management/memory/agent.py

@@ -0,0 +1,41 @@
+# 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.
+
+
+from datetime import datetime
+
+from google.adk import Agent
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.tools.load_memory_tool import load_memory_tool
+from google.adk.tools.preload_memory_tool import preload_memory_tool
+
+
+def update_current_time(callback_context: CallbackContext):
+  callback_context.state['_time'] = datetime.now().isoformat()
+
+
+root_agent = Agent(
+    name='memory_agent',
+    description='agent that have access to memory tools.',
+    before_agent_callback=update_current_time,
+    instruction="""\
+You are an agent that help user answer questions.
+
+Current time: {_time}
+""",
+    tools=[
+        load_memory_tool,
+        preload_memory_tool,
+    ],
+)