minor fix

mmdet/ops/__init__.py

-from .dcn import (DeformConv, DeformRoIPooling, ModulatedDeformRoIPoolingPack,
-                  ModulatedDeformConv, ModulatedDeformConvPack, deform_conv,
-                  modulated_deform_conv, deform_roi_pooling)
+from .dcn import (DeformConv, DeformRoIPooling, DeformRoIPoolingPack,
+                  ModulatedDeformRoIPoolingPack, ModulatedDeformConv,
+                  ModulatedDeformConvPack, deform_conv, modulated_deform_conv,
+                  deform_roi_pooling)
 from .nms import nms, soft_nms
 from .roi_align import RoIAlign, roi_align
 from .roi_pool import RoIPool, roi_pool
 
 __all__ = [
     'nms', 'soft_nms', 'RoIAlign', 'roi_align', 'RoIPool', 'roi_pool',
-    'DeformConv', 'DeformRoIPooling', 'ModulatedDeformRoIPoolingPack',
-    'ModulatedDeformConv', 'ModulatedDeformConvPack', 'deform_conv',
-    'modulated_deform_conv', 'deform_roi_pooling'
+    'DeformConv', 'DeformRoIPooling', 'DeformRoIPoolingPack',
+    'ModulatedDeformRoIPoolingPack', 'ModulatedDeformConv',
+    'ModulatedDeformConvPack', 'deform_conv', 'modulated_deform_conv',
+    'deform_roi_pooling'
 ]

mmdet/ops/dcn/modules/deform_conv.py

@@ -17,8 +17,8 @@ class DeformConv(nn.Module):
                  padding=0,
                  dilation=1,
                  deformable_groups=1,
-                 bias=None):
-        assert bias is None
+                 bias=False):
+        assert not bias
         super(DeformConv, self).__init__()
         self.in_channels = in_channels
         self.out_channels = out_channels