sentence-transformers safetensors electra sentence-similarity feature-extraction generated_from_trainer dataset_size:1115700 loss:MatryoshkaLoss loss:MultipleNegativesRankingLoss arxiv:1908.10084 arxiv:2205.13147 arxiv:1705.00652 base_model:UBC-NLP/serengeti-E250 model-index autotrain_compatible endpoints_compatible region:us