def default_formatter(fields: Optional[dict] = None) -> ReActChatFormatter:
    """Sets up a default formatter so that the proper react header is set."""
    fields = fields or {}
    return ReActChatFormatter.from_defaults(context=fields.get("system_prompt", None))
Sets up a default formatter so that the proper react header is set.
llama-index-core/llama_index/core/agent/workflow/react_agent.py