docs: fix the usage of BuiltInCodeExecutor in code snippets (#503)

* docs: fix the usage of `BuiltInCodeExecutor` in code snippets

* revert stray spaces

---------

Co-authored-by: Lavi Nigam <[email protected]>

Author: shobsi

docs/tools/built-in-tools.md

@@ -117,7 +117,7 @@ to use built-in tools with other tools by using multiple agents:
         instruction="""
         You're a specialist in Code Execution
         """,
-        code_executor=[BuiltInCodeExecutor],
+        code_executor=BuiltInCodeExecutor(),
     )
     root_agent = Agent(
         name="RootAgent",
@@ -204,7 +204,7 @@ to use built-in tools with other tools by using multiple agents:
         model="gemini-2.0-flash",
         description="Root Agent",
         tools=[custom_function], 
-        executor=[BuiltInCodeExecutor] # <-- not supported when used with tools
+        code_executor=BuiltInCodeExecutor() # <-- not supported when used with tools
     )
     ```
 
@@ -244,7 +244,7 @@ is **not** currently supported:
         instruction="""
         You're a specialist in Code Execution
         """,
-        executor=[BuiltInCodeExecutor],
+        code_executor=BuiltInCodeExecutor(),
     )
     root_agent = Agent(
         name="RootAgent",

examples/python/snippets/tools/built-in-tools/code_execution.py

@@ -29,7 +29,7 @@
 code_agent = LlmAgent(
     name=AGENT_NAME,
     model=GEMINI_MODEL,
-    executor=[BuiltInCodeExecutor],
+    code_executor=BuiltInCodeExecutor(),
     instruction="""You are a calculator agent.
     When given a mathematical expression, write and execute Python code to calculate the result.
     Return only the final numerical result as plain text, without markdown or code blocks.
@@ -39,9 +39,9 @@
 
 # Session and Runner
 session_service = InMemorySessionService()
-session = session_service.create_session(
+session = asyncio.run(session_service.create_session(
     app_name=APP_NAME, user_id=USER_ID, session_id=SESSION_ID
-)
+))
 runner = Runner(agent=code_agent, app_name=APP_NAME, session_service=session_service)