Refactor COCO utility functions and test imports

- Simplify import and error handling in `coco.py`
- Clean up import statements in test file
- Minor code formatting improvements

sahi/utils/coco.py

@@ -1357,9 +1357,7 @@ def export_as_yolo(
         try:
             import yaml
         except ImportError:
-            raise ImportError(
-                'Please run "pip install -U pyyaml" to install yaml first for yolo formatted exporting.'
-            )
+            raise ImportError('Please run "pip install -U pyyaml" to install yaml first for yolo formatted exporting.')
 
         # set split_mode
         if 0 < train_split_rate and train_split_rate < 1:
@@ -2401,7 +2399,7 @@ def remove_invalid_coco_results(
     return fixed_result_list
 
 
-def export_coco_as_yolov5(    
+def export_coco_as_yolov5(
     output_dir: str,
     train_coco: Optional[Coco] = None,
     val_coco: Optional[Coco] = None,
@@ -2519,6 +2517,7 @@ def export_coco_as_yolo(
 
     return yaml_path
 
+
 def export_coco_as_yolov5_via_yml(
     yml_path: str, output_dir: str, train_split_rate: float = 0.9, numpy_seed=0, disable_symlink=False
 ):

tests/test_cocoutils.py

@@ -688,8 +688,7 @@ def test_cocovid(self):
         pass
 
     def test_bbox_clipping(self):
-        from sahi.utils.coco import (Coco, CocoAnnotation, CocoCategory,
-                                     CocoImage)
+        from sahi.utils.coco import Coco, CocoAnnotation, CocoCategory, CocoImage
 
         coco = Coco()
         coco.add_category(CocoCategory(id=0, name="box", supercategory="box"))