output_cls parameter of TreeSummarize to extract some common information from my documents. I have metadata in place that will allow me to capture exactly the document subset I want to summarize over. SummaryIndex and then filter on the metadata after retrieval. I also tried using my normal vector store with filters set during retriever creation, but it is hard to create a query that captures all the documents pre-filtering, because there is no default embedding for an empty query and i can't see a place to pass one in (like you can with the VectorIndexAutoRetriever).from llama_index.core import QueryBundle vector_index.query(QueryBundle(query_str="empty", embedding=[0]*embed_dim))