Hey,
As @Nikronic said above, it seems that dataset is a custom module. So, make sure that you have a file called dataset.py within the same directory as your Python script because if it’s not in the same directory Python won’t be able to find it. (Unless you specifically change your working directory, or just copy the file into the same directory as your Python script).
And, within the file dataset.py make sure there’s a class called AdultDataset inside that file. That’s what you’re looking for with the line from dataset import AdultDataset
If this dataset is a file you’ve installed via pip or conda make sure that your Python environment is set to use  the correct environment!
Kind regards,