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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def find_classes(folder:Path)->FilePathList:
    "List of label subdirectories in imagenet-style `folder`."
    classes = [d for d in folder.iterdir()
               if d.is_dir() and not d.name.startswith('.')]
    assert(len(classes)>0)
    return sorted(classes, key=lambda d: d.name)