chore: import upstream snapshot with attribution

contributing/samples/plugin/plugin_basic/count_plugin.py

@@ -0,0 +1,43 @@
+# 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 google.adk.agents.base_agent import BaseAgent
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.models.llm_request import LlmRequest
+from google.adk.plugins.base_plugin import BasePlugin
+
+
+class CountInvocationPlugin(BasePlugin):
+  """A custom plugin that counts agent and tool invocations."""
+
+  def __init__(self) -> None:
+    """Initialize the plugin with counters."""
+    super().__init__(name="count_invocation")
+    self.agent_count: int = 0
+    self.tool_count: int = 0
+    self.llm_request_count: int = 0
+
+  async def before_agent_callback(
+      self, *, agent: BaseAgent, callback_context: CallbackContext
+  ) -> None:
+    """Count agent runs."""
+    self.agent_count += 1
+    print(f"[Plugin] Agent run count: {self.agent_count}")
+
+  async def before_model_callback(
+      self, *, callback_context: CallbackContext, llm_request: LlmRequest
+  ) -> None:
+    """Count LLM requests."""
+    self.llm_request_count += 1
+    print(f"[Plugin] LLM request count: {self.llm_request_count}")