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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 _set_url(self, url):
 """ Set a new URL for the data server. If we're unable to contact the given url, then the original url is kept. """

    original_url = self._url
    try:
      self._update_index(url)
    except:
      self._url = original_url
      raise