code: def check_cython_extensions(self, extensions):
      for ext in extensions:
          for src in ext.sources:
              if not os.path.exists(src):
                  print("{}: -> [{}]".format(ext.name, ext.sources))
                  raise Exception(
                      """Cython-generated file '{}' not found.
                  Cython is required to compile chainercv from a development
                  branch. Please install Cython or
                  download a release package of chainercv.
                  """.format(
                          src
                      )
                  )
  
file_path: chainercv/setup.py
imports: from distutils.core import setup
  import os
  import pkg_resources
  from setuptools.command import sdist
  from setuptools import find_packages
  from distutils.extension import Extension
label_desc: Use image node_id 1 for calling the CheckingBuildExt obj's underlying member method code with example usage: obj.check_cython_extensions(extensions) without return types