transformers safetensors qwen2 text-generation generated_from_trainer trl kto conversational dataset:trl-lib/kto-mix-14k arxiv:2402.01306 base_model:Qwen/Qwen2-0.5B-Instruct base_model:finetune:Qwen/Qwen2-0.5B-Instruct autotrain_compatible text-generation-inference endpoints_compatible region:us