LangChain retrievers backed by the Parallel Search API.
Settings for excerpt extraction.
Fetch policy for cache vs live content.
Domain allow/deny lists and freshness floor for web research.
Apex-domain semantics: include nature.com, not https://www.nature.com.
Wildcards permitted (e.g. .org).
LangChain retriever that returns Parallel Search results as Documents.
Drops in to any RAG pipeline that expects a BaseRetriever. Each
Document.page_content is the joined excerpt list from one Parallel
result; metadata carries url, title, publish_date, search_id,
the original excerpts list, and the query that produced it.
