ultralytics 8.0.77 Ray[Tune] for hyperparameter optimization (#2014)

Co-authored-by: JF Chen <k-2feng@hotmail.com>
Co-authored-by: Ayush Chaurasia <ayush.chaurarsia@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/utils/callbacks/raytune.py

@@ -0,0 +1,17 @@
+try:
+    import ray
+    from ray import tune
+    from ray.air import session
+except (ImportError, AssertionError):
+    tune = None
+
+
+def on_fit_epoch_end(trainer):
+    if ray.tune.is_session_enabled():
+        metrics = trainer.metrics
+        metrics['epoch'] = trainer.epoch
+        session.report(metrics)
+
+
+callbacks = {
+    'on_fit_epoch_end': on_fit_epoch_end, } if tune else {}