Fix YOLOv8 validation when custom dataset yaml is provided (#1528)

* Fix type of data path for the case where a complete path to a yaml file is used

* Style fixes

src/sparseml/yolov8/validators.py

@@ -14,6 +14,7 @@
 
 import json
 from argparse import Namespace
+from pathlib import Path
 
 import torch
 from tqdm import tqdm
@@ -87,6 +88,8 @@ def __call__(self, trainer=None, model=None, training=True):
                 raise FileNotFoundError(
                     emojis(f"Dataset '{self.args.data}' not found ❌")
                 )
+            if isinstance(self.data["path"], str):
+                self.data["path"] = Path(self.data["path"])
 
             if self.device.type == "cpu":
                 self.args.workers = (