func (iter *SparseMatIterator) Next() *SparseNode {
	node := C.cvGetNextSparseNode((*C.CvSparseMatIterator)(iter))
	return (*SparseNode)(node)
}
func (iter *SparseMatIterator) Next() *SparseNode {
	node := C.cvGetNextSparseNode((*C.CvSparseMatIterator)(iter))
	return (*SparseNode)(node)
}
// returns next sparse array node (or NULL if there is no more nodes)