Retrieval

BM25Retriever(*[, count_vectorizer, top_k, ...])	Retrieve the k-nearest neighbors using a lexical search based on BM25.
SemanticRetriever(*, embedding[, top_k])	Retrieve the k-nearest neighbors using a semantic embedding.
RetrieverReranker(*, retrievers, cross_encoder)	Hybrid retriever (lexical and semantic) followed by a cross-encoder reranker.