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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 wait_for_prompt(self, timeout_s=None):
 """Wait for the user to respond to the current prompt. Args: timeout_s: Seconds to wait before raising a PromptUnansweredError. Returns: A string response, or the empty string if text_input was False. Raises: PromptUnansweredError: Timed out waiting for the user to respond. """

    with self._cond:
      if self._prompt:
        if timeout_s is None:
          self._cond.wait(3600 * 24 * 365)
        else:
          self._cond.wait(timeout_s)
      if self._response is None:
        raise PromptUnansweredError
      return self._response