Implement yaml.safe_load() (#2876)

* Implement yaml.safe_load()

* yaml.safe_dump()

utils/plots.py

@@ -323,7 +323,7 @@ def plot_labels(labels, names=(), save_dir=Path(''), loggers=None):
 def plot_evolution(yaml_file='data/hyp.finetune.yaml'):  # from utils.plots import *; plot_evolution()
     # Plot hyperparameter evolution results in evolve.txt
     with open(yaml_file) as f:
-        hyp = yaml.load(f, Loader=yaml.SafeLoader)
+        hyp = yaml.safe_load(f)
     x = np.loadtxt('evolve.txt', ndmin=2)
     f = fitness(x)
     # weights = (f - f.min()) ** 2  # for weighted results