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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 _on_process_error(self, error):
 """ Display child process error in the text edit. """

        if self is None:
            return
        err = PROCESS_ERROR_STRING[error]
        self._formatter.append_message(err + '\r\n', output_format=OutputFormat.ErrorMessageFormat)