Check against PurePath interface

dataset.py

 import os
-from pathlib import Path
+from pathlib import Path, PurePath
 
 import numpy as np
 import pandas as pd
@@ -77,7 +77,7 @@ class NumpyCSVDataset(Dataset):
     ):
         super(NumpyCSVDataset, self).__init__()
 
-        if not isinstance(data_dir, Path):
+        if not isinstance(data_dir, PurePath):
             data_dir = Path(data_dir)
 
         self.data_dir = data_dir