db1 = PGVector.from_existing_index(
    embedding=embeddings,
    collection_name="state_of_the_union",
    distance_strategy=DEFAULT_DISTANCE_STRATEGY,
    pre_delete_collection = False,
    connection_string=CONNECTION_STRING,
)
query = "What did the president say about Ketanji Brown Jackson"
docs_with_score: List[Tuple[Document, float]] = db1.similarity_search_with_score(query)
print(docs_with_score)
rtdocs_stable/api.python.langchain.com/en/stable/modules/indexes/vectorstores/examples/pgvector.html