code: def _to_tensor(self):
      x = self.model_inputs[0].zvalue
      y = self.model_inputs[1].zvalue
      return x - y
  
imports: from zoo.pipeline.api.onnx.mapper.operator_mapper import OperatorMapper
label_desc: Use image node_id 3 for calling the SubMapper obj's underlying member method code with example usage: obj._to_tensor() and returns: unknown