docstr: Returns underlying onnx model of the tree model being used
docstr_tok: ["Returns","underlying","onnx","model","of","the","tree","model","being","used"]
code: def onnx_model(self):
      """Returns underlying onnx model of the tree model being used"""
      return self.__model
  
file_path: OMLT/src/omlt/gbt/model.py
label_desc: Use image node_id 2 for calling the GradientBoostedTreeModel obj's underlying member method code with example usage: obj.onnx_model() and returns: self