chore: import upstream snapshot with attribution

contributing/samples/workflows/loop/agent.py

@@ -0,0 +1,80 @@
+# 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 typing import Literal
+
+from google.adk import Agent
+from google.adk import Event
+from google.adk import Workflow
+from pydantic import BaseModel
+from pydantic import Field
+
+
+class Feedback(BaseModel):
+  grade: Literal["tech-related", "unrelated"] = Field(
+      description=(
+          "Decide if the headline is related to technology or software"
+          " engineering."
+      ),
+  )
+  feedback: str = Field(
+      description=(
+          "If the headline is unrelated to technology, provide feedback on how"
+          " to make it more tech-focused."
+      ),
+  )
+
+
+def process_input(node_input: str):
+  """Puts user input in the state."""
+  return Event(state={"topic": node_input})
+
+
+generate_headline = Agent(
+    name="generate_headline",
+    instruction="""
+    Write a headline about the topic "{topic}".
+    If feedback is provided, take it into account.
+    The feedback: {feedback?}
+    """,
+)
+
+
+evaluate_headline = Agent(
+    name="evaluate_headline",
+    instruction="""
+    Grade whether the headline is related to technology or software engineering.
+    """,
+    output_schema=Feedback,
+    output_key="feedback",
+)
+
+
+def route_headline(node_input: Feedback):
+  return Event(route=node_input.grade)
+
+
+root_agent = Workflow(
+    name="root_agent",
+    edges=[
+        (
+            "START",
+            process_input,
+            generate_headline,
+            evaluate_headline,
+            route_headline,
+        ),
+        (route_headline, {"unrelated": generate_headline}),
+    ],
+)