some renaming

configs/retinanet_r50_fpn_1x.py

@@ -3,7 +3,7 @@ model = dict(
     type='RetinaNet',
     pretrained='modelzoo://resnet50',
     backbone=dict(
-        type='resnet',
+        type='ResNet',
         depth=50,
         num_stages=4,
         out_indices=(0, 1, 2, 3),

mmdet/models/detectors/__init__.py

@@ -5,7 +5,7 @@ from .rpn import RPN
 from .fast_rcnn import FastRCNN
 from .faster_rcnn import FasterRCNN
 from .mask_rcnn import MaskRCNN
-from .retina_net import RetinaNet
+from .retinanet import RetinaNet
 
 __all__ = [
     'BaseDetector', 'SingleStageDetector', 'TwoStageDetector', 'RPN',