pub fn extend<I, J>(&mut self, other: I)
    where
        I: IntoIterator<Item = (ContentOrigin, Vec<CheckableChunk>), IntoIter = J>,
        J: Iterator<Item = (ContentOrigin, Vec<CheckableChunk>)>,
    {
        other
            .into_iter()
            .for_each(|(origin, chunks): (_, Vec<CheckableChunk>)| {
                self.add_inner(origin, chunks);
            });
    }
Extend `self` by joining in other `Documentation`s.
doc-chunks/src/lib.rs