ultralytics 8.0.136 refactor and simplify package (#3748)

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/nn/tasks.py

@@ -11,12 +11,12 @@ from ultralytics.nn.modules import (AIFI, C1, C2, C3, C3TR, SPP, SPPF, Bottlenec
                                     Classify, Concat, Conv, Conv2, ConvTranspose, Detect, DWConv, DWConvTranspose2d,
                                     Focus, GhostBottleneck, GhostConv, HGBlock, HGStem, Pose, RepC3, RepConv,
                                     RTDETRDecoder, Segment)
-from ultralytics.yolo.utils import DEFAULT_CFG_DICT, DEFAULT_CFG_KEYS, LOGGER, colorstr, emojis, yaml_load
-from ultralytics.yolo.utils.checks import check_requirements, check_suffix, check_yaml
-from ultralytics.yolo.utils.loss import v8ClassificationLoss, v8DetectionLoss, v8PoseLoss, v8SegmentationLoss
-from ultralytics.yolo.utils.plotting import feature_visualization
-from ultralytics.yolo.utils.torch_utils import (fuse_conv_and_bn, fuse_deconv_and_bn, initialize_weights,
-                                                intersect_dicts, make_divisible, model_info, scale_img, time_sync)
+from ultralytics.utils import DEFAULT_CFG_DICT, DEFAULT_CFG_KEYS, LOGGER, colorstr, emojis, yaml_load
+from ultralytics.utils.checks import check_requirements, check_suffix, check_yaml
+from ultralytics.utils.loss import v8ClassificationLoss, v8DetectionLoss, v8PoseLoss, v8SegmentationLoss
+from ultralytics.utils.plotting import feature_visualization
+from ultralytics.utils.torch_utils import (fuse_conv_and_bn, fuse_deconv_and_bn, initialize_weights, intersect_dicts,
+                                           make_divisible, model_info, scale_img, time_sync)
 
 try:
     import thop
@@ -412,7 +412,7 @@ class RTDETRDetectionModel(DetectionModel):
 
     def init_criterion(self):
         """Compute the classification loss between predictions and true labels."""
-        from ultralytics.vit.utils.loss import RTDETRDetectionLoss
+        from ultralytics.models.utils.loss import RTDETRDetectionLoss
 
         return RTDETRDetectionLoss(nc=self.nc, use_vfl=True)
 
@@ -498,6 +498,45 @@ class Ensemble(nn.ModuleList):
 # Functions ------------------------------------------------------------------------------------------------------------
 
 
+@contextlib.contextmanager
+def temporary_modules(modules=None):
+    """
+    Context manager for temporarily adding or modifying modules in Python's module cache (`sys.modules`).
+
+    This function can be used to change the module paths during runtime. It's useful when refactoring code,
+    where you've moved a module from one location to another, but you still want to support the old import
+    paths for backwards compatibility.
+
+    Args:
+        modules (dict, optional): A dictionary mapping old module paths to new module paths.
+
+    Example:
+        with temporary_modules({'old.module.path': 'new.module.path'}):
+            import old.module.path  # this will now import new.module.path
+
+    Note:
+        The changes are only in effect inside the context manager and are undone once the context manager exits.
+        Be aware that directly manipulating `sys.modules` can lead to unpredictable results, especially in larger
+        applications or libraries. Use this function with caution.
+    """
+    if not modules:
+        modules = {}
+
+    import importlib
+    import sys
+    try:
+        # Set modules in sys.modules under their old name
+        for old, new in modules.items():
+            sys.modules[old] = importlib.import_module(new)
+
+        yield
+    finally:
+        # Remove the temporary module paths
+        for old in modules:
+            if old in sys.modules:
+                del sys.modules[old]
+
+
 def torch_safe_load(weight):
     """
     This function attempts to load a PyTorch model with the torch.load() function. If a ModuleNotFoundError is raised,
@@ -510,12 +549,17 @@ def torch_safe_load(weight):
     Returns:
         (dict): The loaded PyTorch model.
     """
-    from ultralytics.yolo.utils.downloads import attempt_download_asset
+    from ultralytics.utils.downloads import attempt_download_asset
 
     check_suffix(file=weight, suffix='.pt')
     file = attempt_download_asset(weight)  # search online if missing locally
     try:
-        return torch.load(file, map_location='cpu'), file  # load
+        with temporary_modules({
+                'ultralytics.yolo.utils': 'ultralytics.utils',
+                'ultralytics.yolo.v8': 'ultralytics.models.yolo',
+                'ultralytics.yolo.data': 'ultralytics.data'}):  # for legacy 8.0 Classify and Pose models
+            return torch.load(file, map_location='cpu'), file  # load
+
     except ModuleNotFoundError as e:  # e.name is missing module name
         if e.name == 'models':
             raise TypeError(