ChunkedIterator: Splits an iterator into chunks based on a given block size.
ClosableIterator: An AsyncIterator with a callback for when this iterator is closed in any way. In contrast to ClosableTransformIterator, this does not add the overhead of a TransformIterator.
ClosableTransformIterator: A TransformIterator with a callback for when this iterator is closed in any way.
instrumentIterator: Profile an iterator by monkey-patching its _read and read methods.