Testing images from a separate folder in tensorflow

I retrained my own inception_v3 model like in the tensorflow-for-poets codelab. Within this tutorial it is possible to test the model on individual images and the final test accuracy is output when the retrain script is called. However this test accuracy is done by on images that were separated from the training set. I'd like to ask how I could run the test on images from a separate folder (as I want to carry out Person Independent test), if possible within Docker?

Retrain script: https://github.com/googlecodelabs/tensorflow-for-poets-2/blob/master/scripts/retrain.py