Fix: Set output_schema correctly for LiteLllm

Author: whoisarpit

src/google/adk/models/lite_llm.py

@@ -447,7 +447,7 @@ def _get_completion_inputs(
     llm_request: The LlmRequest to convert.
 
   Returns:
-    The litellm inputs (message list and tool dictionary).
+    The litellm inputs (message list, tool dictionary and response format).
   """
   messages = []
   for content in llm_request.contents or []:
@@ -476,7 +476,13 @@ def _get_completion_inputs(
         _function_declaration_to_tool_param(tool)
         for tool in llm_request.config.tools[0].function_declarations
     ]
-  return messages, tools
+
+  response_format = None
+
+  if llm_request.config.response_schema:
+    response_format = llm_request.config.response_schema
+
+  return messages, tools, response_format
 
 
 def _build_function_declaration_log(
@@ -613,12 +619,13 @@ async def generate_content_async(
     self._maybe_append_user_content(llm_request)
     logger.info(_build_request_log(llm_request))
 
-    messages, tools = _get_completion_inputs(llm_request)
+    messages, tools, response_format = _get_completion_inputs(llm_request)
 
     completion_args = {
         "model": self.model,
         "messages": messages,
         "tools": tools,
+        "response_format": response_format,
     }
     completion_args.update(self._additional_args)