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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 sign_out(self, redirect_url=None):
 """Returns a signed URL to disassociate the ouath2 user from the session."""

    config = config_lib.get_config()
    key = self.handler.app.config['webapp2_extras.sessions']['secret_key']
    if redirect_url is None:
      redirect_url = self.handler.request.url
    user_id = self.handler.me.user_id()
    token = xsrfutil.generate_token(key, user_id, action_id=redirect_url)
    return '{}/signout?{}'.format(config['airlock_path'], urllib.urlencode({
        'redirect': redirect_url,
        'token': token,
    }))