code: def _to_tensor(self):
      x = self.model_inputs[0]
      y = self.model_inputs[1]
      return zautograd.mm(x.zvalue, y.zvalue)
  
file_path: analytics-zoo/pyzoo/zoo/pipeline/api/onnx/mapper/matmul.py
imports: from zoo.pipeline.api.onnx.mapper.operator_mapper import OperatorMapper
  from zoo.pipeline.api.onnx.onnx_helper import OnnxHelper
  import zoo.pipeline.api.keras.layers
  import zoo.pipeline.api.autograd
  import numpy
label_desc: Use image node_id 3 for calling the MatMulMapper obj's underlying member method code with example usage: obj._to_tensor() and returns: zautograd