code: def _to_tensor(self):
      return self.model_inputs[0].zvalue
  
file_path: analytics-zoo/pyzoo/zoo/pipeline/api/onnx/mapper/constant.py
imports: import bigdl.nn.layer
  import numpy
  import zoo.pipeline.api.keras.layers
  from zoo.pipeline.api.onnx.mapper.operator_mapper import OperatorMapper
  from zoo.pipeline.api.onnx.onnx_helper import OnnxHelper
  from zoo.pipeline.api.onnx.onnx_loader import OnnxInput
label_desc: Use image node_id 3 for calling the ConstantMapper obj's underlying member method code with example usage: obj._to_tensor() and returns: self