Add new checkpoint

Hello,
I think you miss one checkpoint given that endpoints['reduction_5'] is the head of the network but not the last layer of the backbone. This may be problematic if we use you implementation of EfficientNet as backbone of EfficientDet.
In this PR, I let the checkpoint of the head (endpoints['reduction_6']) but changed endpoints['reduction_5'] accordingly.
If I'm wrong let me know.
Regards,
Renaud

Author: rvandeghen

efficientnet_pytorch/model.py

@@ -248,7 +248,8 @@ def extract_endpoints(self, inputs):
                 >>> print(endpoints['reduction_2'].shape)  # torch.Size([1, 24, 56, 56])
                 >>> print(endpoints['reduction_3'].shape)  # torch.Size([1, 40, 28, 28])
                 >>> print(endpoints['reduction_4'].shape)  # torch.Size([1, 112, 14, 14])
-                >>> print(endpoints['reduction_5'].shape)  # torch.Size([1, 1280, 7, 7])
+                >>> print(endpoints['reduction_5'].shape)  # torch.Size([1, 320, 7, 7])
+                >>> print(endpoints['reduction_6'].shape)  # torch.Size([1, 1280, 7, 7])
         """
         endpoints = dict()
 
@@ -264,6 +265,8 @@ def extract_endpoints(self, inputs):
             x = block(x, drop_connect_rate=drop_connect_rate)
             if prev_x.size(2) > x.size(2):
                 endpoints['reduction_{}'.format(len(endpoints)+1)] = prev_x
+            elif idx == len(self._blocks) - 1:
+                endpoints['reduction_{}'.format(len(endpoints)+1)] = x
             prev_x = x
 
         # Head