General cleanup (#69)

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>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/yolo/engine/model.py

@@ -4,6 +4,7 @@ Top-level YOLO model interface. First principle usage example - https://github.c
 import torch
 import yaml
 
+from ultralytics import yolo
 from ultralytics.yolo.utils import LOGGER
 from ultralytics.yolo.utils.checks import check_yaml
 from ultralytics.yolo.utils.modeling import attempt_load_weights

ultralytics/yolo/engine/trainer.py

@@ -327,7 +327,7 @@ class BaseTrainer:
         metrics = self.validator(self)
         fitness = metrics.pop("fitness", -self.loss.detach().cpu().numpy())  # use loss as fitness measure if not found
         if not self.best_fitness or self.best_fitness < fitness:
-            self.best_fitness = self.fitness
+            self.best_fitness = fitness
         return metrics, fitness
 
     def log(self, text, rank=-1):