Fix `NameError: name 'cfg' is not defined` in roi_box_predictors.py (#407)

maskrcnn_benchmark/modeling/roi_heads/box_head/roi_box_predictors.py

@@ -14,7 +14,7 @@ class FastRCNNPredictor(nn.Module):
         num_classes = config.MODEL.ROI_BOX_HEAD.NUM_CLASSES
         self.avgpool = nn.AvgPool2d(kernel_size=7, stride=7)
         self.cls_score = nn.Linear(num_inputs, num_classes)
-        num_bbox_reg_classes = 2 if cfg.MODEL.CLS_AGNOSTIC_BBOX_REG else num_classes
+        num_bbox_reg_classes = 2 if config.MODEL.CLS_AGNOSTIC_BBOX_REG else num_classes
         self.bbox_pred = nn.Linear(num_inputs, num_bbox_reg_classes * 4)
 
         nn.init.normal_(self.cls_score.weight, mean=0, std=0.01)