feat: support realtime input config

Merge https://github.com/google/adk-python/pull/981

issue: https://github.com/google/adk-python/issues/982

This pull request introduces a new configuration option, `realtime_input_config`, to the `RunConfig` class.

**Reason for this change:**

Currently, there is no direct way to configure real-time audio input behaviors, such as Voice Activity Detection (VAD), for live agents through the `RunConfig`. The Gemini API documentation (specifically [Configure automatic VAD](https://ai.google.dev/gemini-api/docs/live#configure-automatic-vad)) outlines parameters for VAD that users may want to customize.

This change enables users to pass these real-time input configurations, providing more granular control over the audio input for live agents.

**Changes made:**

- Added a new optional field `realtime_input_config: Optional[types.RealtimeInputConfig]` to the `RunConfig` class.
- The docstring for `realtime_input_config` has been added to explain its purpose.

**Example Usage (Conceptual):**

While the specific structure of `types.RealtimeInputConfig` would define the exact parameters, a user might configure it like this:

```python
# (Assuming types.RealtimeInputConfig and types.VadConfig are defined elsewhere)
# import your_project.types as types

run_config = RunConfig(
    # ... other configurations ...
    realtime_input_config=types.RealtimeInputConfig(
        automatic_activity_detection =types.AutomaticActivityDetection(
            # VAD specific parameters like sensitivity, endpoint_duration_millis etc.
            # based on https://ai.google.dev/gemini-api/docs/live#configure-automatic-vad
        )
        # Potentially other real-time input settings could be added here in the future
    )
)
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/981 from ammmr:patch-add-realtime-input-config b2e17fbf5742d264029ad49bf632422b5c5b1e0a
PiperOrigin-RevId: 770797640

tests/unittests/models/test_gemini_llm_connection.py

@@ -0,0 +1,111 @@
+# 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
+#
+#     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 unittest import mock
+
+from google.adk.models.gemini_llm_connection import GeminiLlmConnection
+from google.genai import types
+import pytest
+
+
+@pytest.fixture
+def mock_gemini_session():
+  """Mock Gemini session for testing."""
+  return mock.AsyncMock()
+
+
+@pytest.fixture
+def gemini_connection(mock_gemini_session):
+  """GeminiLlmConnection instance with mocked session."""
+  return GeminiLlmConnection(mock_gemini_session)
+
+
+@pytest.fixture
+def test_blob():
+  """Test blob for audio data."""
+  return types.Blob(data=b'\x00\xFF\x00\xFF', mime_type='audio/pcm')
+
+
+@pytest.mark.asyncio
+async def test_send_realtime_default_behavior(
+    gemini_connection, mock_gemini_session, test_blob
+):
+  """Test send_realtime with default automatic_activity_detection value (True)."""
+  await gemini_connection.send_realtime(test_blob)
+
+  # Should call send once
+  mock_gemini_session.send.assert_called_once_with(input=test_blob.model_dump())
+
+
+@pytest.mark.asyncio
+async def test_send_history(gemini_connection, mock_gemini_session):
+  """Test send_history method."""
+  history = [
+      types.Content(role='user', parts=[types.Part.from_text(text='Hello')]),
+      types.Content(
+          role='model', parts=[types.Part.from_text(text='Hi there!')]
+      ),
+  ]
+
+  await gemini_connection.send_history(history)
+
+  mock_gemini_session.send.assert_called_once()
+  call_args = mock_gemini_session.send.call_args[1]
+  assert 'input' in call_args
+  assert call_args['input'].turns == history
+  assert call_args['input'].turn_complete is False  # Last message is from model
+
+
+@pytest.mark.asyncio
+async def test_send_content_text(gemini_connection, mock_gemini_session):
+  """Test send_content with text content."""
+  content = types.Content(
+      role='user', parts=[types.Part.from_text(text='Hello')]
+  )
+
+  await gemini_connection.send_content(content)
+
+  mock_gemini_session.send.assert_called_once()
+  call_args = mock_gemini_session.send.call_args[1]
+  assert 'input' in call_args
+  assert call_args['input'].turns == [content]
+  assert call_args['input'].turn_complete is True
+
+
+@pytest.mark.asyncio
+async def test_send_content_function_response(
+    gemini_connection, mock_gemini_session
+):
+  """Test send_content with function response."""
+  function_response = types.FunctionResponse(
+      name='test_function', response={'result': 'success'}
+  )
+  content = types.Content(
+      role='user', parts=[types.Part(function_response=function_response)]
+  )
+
+  await gemini_connection.send_content(content)
+
+  mock_gemini_session.send.assert_called_once()
+  call_args = mock_gemini_session.send.call_args[1]
+  assert 'input' in call_args
+  assert call_args['input'].function_responses == [function_response]
+
+
+@pytest.mark.asyncio
+async def test_close(gemini_connection, mock_gemini_session):
+  """Test close method."""
+  await gemini_connection.close()
+
+  mock_gemini_session.close.assert_called_once()