Revert "Remove dataset_stats() autodownload capability (ultralytics#6303)" (ultralytics#6442)

This reverts commit 5aa3534.

Author: glenn-jocher

utils/datasets.py

@@ -936,10 +936,11 @@ def verify_image_label(args):
         return [None, None, None, None, nm, nf, ne, nc, msg]
 
 
-def dataset_stats(path='coco128.yaml', verbose=False, profile=False, hub=False):
+def dataset_stats(path='coco128.yaml', autodownload=False, verbose=False, profile=False, hub=False):
     """ Return dataset statistics dictionary with images and instances counts per split per class
     To run in parent directory: export PYTHONPATH="$PWD/yolov5"
-    Usage: from utils.datasets import *; dataset_stats('../datasets/coco128_with_yaml.zip')
+    Usage1: from utils.datasets import *; dataset_stats('coco128.yaml', autodownload=True)
+    Usage2: from utils.datasets import *; dataset_stats('../datasets/coco128_with_yaml.zip')
     Arguments
         path:           Path to data.yaml or data.zip (with data.yaml inside data.zip)
         autodownload:   Attempt to download dataset if not found locally
@@ -983,7 +984,7 @@ def hub_ops(f, max_dim=1920):
         data = yaml.safe_load(f)  # data dict
         if zipped:
             data['path'] = data_dir  # TODO: should this be dir.resolve()?
-    check_dataset(data, autodownload=False)
+    check_dataset(data, autodownload)  # download dataset if missing
     hub_dir = Path(data['path'] + ('-hub' if hub else ''))
     stats = {'nc': data['nc'], 'names': data['names']}  # statistics dictionary
     for split in 'train', 'val', 'test':