code: def _check_available():
      if not _available:
          raise ImportError(
              "ONNX is not installed on your environment. Exporting your model "
              "in ONNX format needs the onnx package.\n\n"
              "\t$ pip install 'onnx<1.7.0'\n\n"
          )
  
file_path: chainer/onnx_chainer/export.py
imports: from __future__ import print_function
  from collections import OrderedDict
  import warnings
  import chainer
label_desc: Use image node_id 1 for calling a global function with example usage: _check_available() without return types