Remove unused import of PurePath from base_dataset.py

Author: wli51

src/virtual_stain_flow/datasets/base_dataset.py

@@ -8,7 +8,7 @@
 
 from typing import Dict, Sequence, Optional, Tuple, Union, Any
 import json
-from pathlib import Path, PurePath
+from pathlib import Path
 
 import numpy as np
 import pandas as pd