use crate DocSet;
/// Postings (also called inverted list)
///
/// For a given term, it is the list of doc ids of the doc
/// containing the term. Optionally, for each document,
/// it may also give access to the term frequency
/// as well as the list of term positions.
///
/// Its main implementation is `SegmentPostings`,
/// but other implementations mocking `SegmentPostings` exist,
/// for merging segments or for testing.