� classN       # folder containing documents of class N
    │   └── test
    │       ├── class0       # folder containing documents of class 0
    │       ├── class1       # folder containing documents of class 1
    │       ├── class2       # folder containing documents of class 2
    │       └── classN       # folder containing documents of class N

    Each subfolder should contain documents in plain text format.
    If train and test contain additional subfolders 