Implement yaml.safe_load() (#2876)

* Implement yaml.safe_load()

* yaml.safe_dump()

test.py

@@ -71,7 +71,7 @@ def test(data,
     if isinstance(data, str):
         is_coco = data.endswith('coco.yaml')
         with open(data) as f:
-            data = yaml.load(f, Loader=yaml.SafeLoader)
+            data = yaml.safe_load(f)
     check_dataset(data)  # check
     nc = 1 if single_cls else int(data['nc'])  # number of classes
     iouv = torch.linspace(0.5, 0.95, 10).to(device)  # iou vector for mAP@0.5:0.95