How to do the indexing of voxels in pcl?

I need to access the voxels in voxel grid through indexing, for an example v[1][2][3] and points inside the voxel.

I have been doing the search for the last two days, but I could not able to find any hint or solution to achieve my objective. Using below code, I can get the voxels and their points through iterator, but I need to do it through indexing in pcl.

Part of the code for better explanation:

OctreePointCloudPointVector<pcl::PointXYZ>::LeafNodeIterator itLeafs:
 
for(itLeafs =octree.leaf_begin();itLeafs!=octree.leaf_end();++itLeafs){
    std::vector<int>indices;
    itLeafs.getLeafContainer().getPointIndices(indices); // get the points in the voxel
    }

Is there any good way to access the voxel through indexing? Any third party implementation also fine.

Thanks in advance