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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 mark_failed(self, dispatch, error_log):
 """Marks a dispatch as failed. Sitemessage won't try to deliver already failed messages. Should be used within send(). :param Dispatch dispatch: a Dispatch :param str error_log: str - error message """

        dispatch.error_log = error_log
        self._st['failed'].append(dispatch)