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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def just_find_proxy(pacfile, url, host=None):
 """ This function is a wrapper around init, parse_pac, find_proxy and cleanup. This is the function to call if you want to find proxy just for one url. """

  if not os.path.isfile(pacfile):
    raise IOError('Pac file does not exist: {}'.format(pacfile))
  init()
  parse_pac(pacfile)
  proxy = find_proxy(url,host)
  cleanup()
  return proxy