remove BC-breaking changes (#1560)

* remove changes that induced BC

* Re-enable tests that have been disabled

* Remove outdated comment

* Remove outdated comment

Author: eellison

torchvision/models/_utils.py

@@ -5,7 +5,7 @@
 from torch.jit.annotations import Dict
 
 
-class IntermediateLayerGetter(nn.Module):
+class IntermediateLayerGetter(nn.ModuleDict):
     """
     Module wrapper that returns intermediate layers from a model
 
@@ -45,8 +45,6 @@ class IntermediateLayerGetter(nn.Module):
     def __init__(self, model, return_layers):
         if not set(return_layers).issubset([name for name, _ in model.named_children()]):
             raise ValueError("return_layers are not present in model")
-        super(IntermediateLayerGetter, self).__init__()
-
         orig_return_layers = return_layers
         return_layers = {k: v for k, v in return_layers.items()}
         layers = OrderedDict()
@@ -57,33 +55,14 @@ def __init__(self, model, return_layers):
             if not return_layers:
                 break
 
-        self.layers = nn.ModuleDict(layers)
+        super(IntermediateLayerGetter, self).__init__(layers)
         self.return_layers = orig_return_layers
 
     def forward(self, x):
         out = OrderedDict()
-        for name, module in self.layers.items():
+        for name, module in self.items():
             x = module(x)
             if name in self.return_layers:
                 out_name = self.return_layers[name]
                 out[out_name] = x
         return out
-
-    @torch.jit.ignore
-    def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict,
-                              missing_keys, unexpected_keys, error_msgs):
-        version = local_metadata.get('version', None)
-        if (version is None or version < 2):
-            # now we have a new nesting level for torchscript support
-            for new_key in self.state_dict().keys():
-                # remove prefix "layers."
-                old_key = new_key[len("layers."):]
-                old_key = prefix + old_key
-                new_key = prefix + new_key
-                if old_key in state_dict:
-                    value = state_dict[old_key]
-                    del state_dict[old_key]
-                    state_dict[new_key] = value
-        super(IntermediateLayerGetter, self)._load_from_state_dict(
-            state_dict, prefix, local_metadata, strict,
-            missing_keys, unexpected_keys, error_msgs)

torchvision/models/densenet.py

@@ -90,13 +90,12 @@ def forward(self, input):  # noqa: F811
         return new_features
 
 
-class _DenseBlock(nn.Module):
+class _DenseBlock(nn.ModuleDict):
     _version = 2
     __constants__ = ['layers']
 
     def __init__(self, num_layers, num_input_features, bn_size, growth_rate, drop_rate, memory_efficient=False):
         super(_DenseBlock, self).__init__()
-        self.layers = nn.ModuleDict()
         for i in range(num_layers):
             layer = _DenseLayer(
                 num_input_features + i * growth_rate,
@@ -105,34 +104,15 @@ def __init__(self, num_layers, num_input_features, bn_size, growth_rate, drop_ra
                 drop_rate=drop_rate,
                 memory_efficient=memory_efficient,
             )
-            self.layers['denselayer%d' % (i + 1)] = layer
+            self.add_module('denselayer%d' % (i + 1), layer)
 
     def forward(self, init_features):
         features = [init_features]
-        for name, layer in self.layers.items():
+        for name, layer in self.items():
             new_features = layer(features)
             features.append(new_features)
         return torch.cat(features, 1)
 
-    @torch.jit.ignore
-    def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict,
-                              missing_keys, unexpected_keys, error_msgs):
-        version = local_metadata.get('version', None)
-        if (version is None or version < 2):
-            # now we have a new nesting level for torchscript support
-            for new_key in self.state_dict().keys():
-                # remove prefix "layers."
-                old_key = new_key[len("layers."):]
-                old_key = prefix + old_key
-                new_key = prefix + new_key
-                if old_key in state_dict:
-                    value = state_dict[old_key]
-                    del state_dict[old_key]
-                    state_dict[new_key] = value
-        super(_DenseBlock, self)._load_from_state_dict(
-            state_dict, prefix, local_metadata, strict,
-            missing_keys, unexpected_keys, error_msgs)
-
 
 class _Transition(nn.Sequential):
     def __init__(self, num_input_features, num_output_features):