func (itr *Iterator) Seek(key []byte) {
	if !itr.reversed {
		itr.seek(key)
	} else {
		itr.seekForPrev(key)
	}
}
func (itr *Iterator) Seek(key []byte) {
	if !itr.reversed {
		itr.seek(key)
	} else {
		itr.seekForPrev(key)
	}
}
// Seek follows the y.Iterator interface