pytorch qwen2 Qwen Qwen2.5 0.5B Llama-cpp text-generation conversational en dataset:HuggingFaceH4/ultrachat_200k base_model:unsloth/Qwen2.5-0.5B-bnb-4bit base_model:finetune:unsloth/Qwen2.5-0.5B-bnb-4bit license:creativeml-openrail-m region:us