def _extend_messages(self, messages: List[ChatMessage]) -> List[ChatMessage]:
        """Add system prompt to chat message list."""
        if self.system_prompt:
            messages = [
                ChatMessage(role=MessageRole.SYSTEM, content=self.system_prompt),
                *messages,
            ]
        return messages
Add system prompt to chat message list.
llama-index-core/llama_index/core/llms/llm.py