Copybara import of the project:

--
ad923c2c8c503ba73c62db695e88f1a3ea1aeeea by YU MING HSU <abego452@gmail.com>:

docs: enhance Contribution process within CONTRIBUTING.md

--
8022924fb7e975ac278d38fce3b5fd593d874536 by YU MING HSU <abego452@gmail.com>:

fix: move _maybe_append_user_content from google_llm.py to base_llm.py,
so subclass can get benefit from it, call _maybe_append_user_content
from generate_content_async within lite_llm.py

--
cf891fb1a3bbccaaf9d0055b23f614ce52449977 by YU MING HSU <abego452@gmail.com>:

fix: modify install dependencies cmd, and use pyink to format codebase
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/428 from hsuyuming:fix_litellm_error_issue_427 dbec4949798e6399a0410d1b8ba7cc6a7cad7bdd
PiperOrigin-RevId: 754124679

src/google/adk/flows/__init__.py

@@ -11,4 +11,3 @@
 # 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.
-

src/google/adk/flows/llm_flows/functions.py

@@ -332,7 +332,7 @@ async def _process_function_live_helper(
       function_response = {
           'status': f'No active streaming function named {function_name} found'
       }
-  elif hasattr(tool, "func") and inspect.isasyncgenfunction(tool.func):
+  elif hasattr(tool, 'func') and inspect.isasyncgenfunction(tool.func):
     # for streaming tool use case
     # we require the function to be a async generator function
     async def run_tool_and_update_queue(tool, function_args, tool_context):