What is the purpose of the following code:

[tomoya-kunnnnnn]

in function markerMatch() for pruning in Dynamicvoronoi.cpp, we have the following code:
'''
if (voroCount<3 && voroCountFour==1 && (f[1] || f[3] || f[4] || f[6])) {
return keep;
}
'''
so can you explain or give me related articles about what is the purpose of them, as I did not find related explanation on related papers.