iterator

type Interface[K, V any] interface {
	// Next returns the next key/value pair, where the key is a slice index, map key, document number, etc,
	// and the value is the slice or map value, next document, etc.
	//
	// Returned error could be (possibly wrapped) ErrIteratorDone or some fatal error
	// like (possibly wrapped) context.Canceled.
	// In any case, even if iterator was read to the end, and Next returned ErrIteratorDone,
	// or Next returned fatal error,
	// Close method still should be called.
	//
	// Next should not be called concurrently.
	Next() (K, V, error)

	// Close indicates that the iterator will no longer be used.
	// After Close is called, future calls to Next must return ErrIteratorDone,
	// even if previous call returned a different error.
	//
	// Close must be called.
	// If it wasn't, the iterator might leak resources or panic later.
	//
	// Close must be concurrency-safe and may be called multiple times.
	// All calls after the first should have no observable effect.
	Close()
}