Revert function in palabos

Dear Palabos developers,

I am a beginner with Palabos. I am having a trouble to understand the revert function in Palabos. It is not connected well to the document I found in the report #1.

In cell::revert()
for (plint iPop=1; iPop<=Descriptor::q/2; ++iPop) {

For me it is only reverted inside this cell. Not as what is mentioned in the report #1:

for (int iF=1; iF<=half; ++iF) {
nextX = iX + c[iF][0];
nextY = iY + c[iF][1];
if (nextX>=0 && nextY>=0 && nextX<lx && nextY<ly) {
swap(f[iX][iY][iF+half], f[nextX][nextY][iF]); <----------- swap between two lattices

Could please show me the way Palabos did?
Thank you very much for your time,
/ Ming Q.