docs: update code example

Author: dkundel-openai

docs/format.md

@@ -52,13 +52,8 @@ encoding = load_harmony_encoding(HarmonyEncodingName.HARMONY_GPT_OSS)
 
 system_message = (
     SystemContent.new()
-        .with_model_identity(
-            "You are ChatGPT, a large language model trained by OpenAI."
-        )
         .with_reasoning_effort(ReasoningEffort.HIGH)
         .with_conversation_start_date("2025-06-28")
-        .with_knowledge_cutoff("2024-06")
-        .with_required_channels(["analysis", "commentary", "final"])
 )
 
 developer_message = (
@@ -101,11 +96,11 @@ convo = Conversation.from_messages(
         Message.from_role_and_content(Role.ASSISTANT, '{"location": "Tokyo"}')
         .with_channel("commentary")
         .with_recipient("functions.get_weather")
-        .with_content_type("json"),
+        .with_content_type("<|constrain|> json"),
         Message.from_author_and_content(
             Author.new(Role.TOOL, "functions.lookup_weather"),
             '{ "temperature": 20, "sunny": true }',
-        ),
+        ).with_channel("commentary"),
     ]
 )