sentence-transformers safetensors bert sentence-similarity feature-extraction loss:MSELoss en arxiv:1908.10084 arxiv:2004.09813 base_model:nreimers/TinyBERT_L-4_H-312_v2 base_model:finetune:nreimers/TinyBERT_L-4_H-312_v2 model-index co2_eq_emissions autotrain_compatible text-embeddings-inference endpoints_compatible region:us