examples/pytorch/text-generation/run_generation.py/prepare_ctrl_input
def prepare_ctrl_input(args, _, tokenizer, prompt_text):
    if args.temperature > 0.7:
        logger.info("CTRL typically works better with lower temperatures (and lower top_k).")

    encoded_prompt = tokenizer.encode(prompt_text, add_special_tokens=False)
    if not any(encoded_prompt[0] == x for x in tokenizer.control_codes.values()):
        logger.info("WARNING! You are not starting your generation from a control code so you won't get good results")
    return prompt_text