gguf RLHF Nexusflow Athene Chat Model quantized GGUF quantization imat imatrix static 16bit 8bit 6bit 5bit 4bit 3bit 2bit 1bit text-generation en base_model:Nexusflow/Athene-70B base_model:quantized:Nexusflow/Athene-70B license:cc-by-nc-4.0 region:us