def train(self, mode=True):
        """Convert the model into training mode while keep normalization layer
        freezed."""
        super(VoVNet, self).train(mode)
        self._freeze_stages()
        if mode and self.norm_eval:
            for m in self.modules():
                # trick: eval have effect on BatchNorm only
                if isinstance(m, _BatchNorm):
                    m.eval()
Convert the model into training mode while keep normalization layer
        freezed.
projects/mmdet3d_plugin/models/backbones/vovnet.py