How to know the index of my labels

In the person detection example, from the book, in model settings, the labels are hard coded to the index:

constexpr int kCategoryCount = 3;
constexpr int kPersonIndex = 1;
constexpr int kNotAPersonIndex = 2;

const char* kCategoryLabels[ kCategoryCount] = { “unused”, “person”, “notperson”,}

How can I confirm that kPersonIndex=1 and kNotAPersonIndex=2, and not the other way around?