docstr: Save ONNXRuntimeModel to local as an onnx file
  
  :param path: Path to save the model.
docstr_tok: ["Save","ONNXRuntimeModel","to","local","as","an","onnx","file",":","param","path",":","Path","to","save","the","model","."]
code: def _save_model(self, path, compression="fp32"):
      """
      Save ONNXRuntimeModel to local as an onnx file
  
      :param path: Path to save the model.
      """
      path = Path(path)
      invalidInputError(
          self.onnx_model, "self.ie_network shouldn't be None."
      )
      invalidInputError(
          path.suffix == ".onnx",
          "Path of onnx model must be with '.onnx' suffix.",
      )
      onnx.save(self.onnx_model, str(path))
  
file_path: BigDL/python/nano/src/bigdl/nano/deps/onnxruntime/core/onnxruntime_model.py
imports: from pathlib import Path
  import onnxruntime
  import onnx
  from bigdl.nano.utils.common import invalidInputError, _flatten
  import numpy
label_desc: Use image node_id 5 for calling the ONNXRuntimeModel obj's underlying member method code with example usage: obj._save_model(path, compression) without return types