message: add sum of 1 input
diff: @@ -929,6 +929,14 @@ void ONNXImporter::parseBias(LayerParams& layerParams, const opencv_onnx::NodePr
  opencv_onnx::NodeProto node_proto = node_proto_;
  const std::string& layer_type = node_proto.op_type();
  bool isSub = layer_type == "Sub";
  +
  + if (layer_type == "Sum" && node_proto.input_size() == 1)
  + {
  + layerParams.type = "Identity";
  + addLayer(layerParams, node_proto);
  + return;
  + }
  +
  CV_Assert((node_proto.input_size() == 2) || (layer_type == "Sum" && node_proto.input_size() > 2));
  if (layer_type == "Sum" && node_proto.input_size() > 2)
  