code: def _format_add_colon_two(
      system_message: str,
      messages: List[Tuple[str, Optional[str]]],
      sep: str,
      sep2: str,
  ) -> str:
      """Format the prompt with the add-colon-two style."""
      seps = [sep, sep2]
      ret = system_message + seps[0]
      for i, (role, message) in enumerate(messages):
          if message:
              ret += role + ": " + message + seps[i % 2]
          else:
              ret += role + ":"
      return ret
  
imports: from __future__ import annotations
  import os
  import json
  import ctypes
  import dataclasses
  from typing import Any, Dict, Iterator, List, Optional, Tuple, Union, Protocol
  import llama_cpp.llama
  import llama_cpp.llama_types
  import llama_cpp.llama_grammar
  from ._utils import suppress_stdout_stderr
label_desc: Use image node_id 7 for calling a global function with example usage: _format_add_colon_two(system_message, messages, sep, sep2) and returns: ret