transformers gguf mergekit merge arxiv:2306.01708 base_model:Qwen/Qwen2.5-7B base_model:merge:Qwen/Qwen2.5-7B base_model:Qwen/Qwen2.5-7B-Instruct base_model:merge:Qwen/Qwen2.5-7B-Instruct endpoints_compatible region:us conversational