chore: Defer import of live, Client and _transformers in google.genai

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 831444358

src/google/adk/models/google_llm.py

@@ -27,7 +27,6 @@ from typing import Optional
 from typing import TYPE_CHECKING
 from typing import Union
 
-from google.genai import Client
 from google.genai import types
 from typing_extensions import override
 
@@ -41,6 +40,8 @@ from .gemini_llm_connection import GeminiLlmConnection
 from .llm_response import LlmResponse
 
 if TYPE_CHECKING:
+  from google.genai import Client
+
   from .llm_request import LlmRequest
 
 logger = logging.getLogger('google_adk.' + __name__)
@@ -200,6 +201,8 @@ class Gemini(BaseLlm):
     Returns:
       The api client.
     """
+    from google.genai import Client
+
     return Client(
         http_options=types.HttpOptions(
             headers=self._tracking_headers,
@@ -239,6 +242,8 @@ class Gemini(BaseLlm):
 
   @cached_property
   def _live_api_client(self) -> Client:
+    from google.genai import Client
+
     return Client(
         http_options=types.HttpOptions(
             headers=self._tracking_headers, api_version=self._live_api_version