sentence-transformers safetensors nomic_bert sentence-similarity feature-extraction dataset_size:100K<n<1M loss:CachedMultipleNegativesRankingLoss custom_code arxiv:1908.10084 arxiv:2101.06983 base_model:nomic-ai/nomic-embed-text-v1.5 base_model:finetune:nomic-ai/nomic-embed-text-v1.5 model-index autotrain_compatible text-embeddings-inference endpoints_compatible region:us