Update download_model.py

pretrained_model/download_model.py

@@ -92,6 +92,8 @@ model_urls = {
     "https://paddleseg.bj.bcebos.com/models/hrnet_w18_bn_cityscapes.tgz",
     "fast_scnn_cityscapes":
     "https://paddleseg.bj.bcebos.com/models/fast_scnn_cityscape.tar",
+    "ocnet_w18_bn_cityscapes":
+    "https://paddleseg.bj.bcebos.com/models/ocnet_w18_bn_cityscapes.tar.gz",
 }
 
 if __name__ == "__main__":