Implement yaml.safe_load() (#2876)

* Implement yaml.safe_load()

* yaml.safe_dump()

models/yolo.py

@@ -72,7 +72,7 @@ class Model(nn.Module):
             import yaml  # for torch hub
             self.yaml_file = Path(cfg).name
             with open(cfg) as f:
-                self.yaml = yaml.load(f, Loader=yaml.SafeLoader)  # model dict
+                self.yaml = yaml.safe_load(f)  # model dict
 
         # Define model
         ch = self.yaml['ch'] = self.yaml.get('ch', ch)  # input channels