deeplabv3+ mean subtraction implementated?

Question

I'm currently using deeplabv3+ on my own dataset, therefore I took a closer look at code of some utility functions for preprocessing. It seems, that the mean subtraction is defined in feature_extractor.py but not used in input_preprocess.py which is called by input_generator.py. The train.py does not do the mean subtraction either, it just calls input_generator where no mean subtraction function is called. I'm wondering did I miss something? Is it implemented in somewhere else or? Thanks for the reply!