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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 _ensure_opened(self):
 """Start monitors, or restart after a fork. Hold the lock when calling this. """

        if not self._opened:
            self._opened = True
            self._update_servers()

            # Start or restart the events publishing thread.
            if self._publish_tp or self._publish_server:
                self.__events_executor.open()

        # Ensure that the monitors are open.
        for server in itervalues(self._servers):
            server.open()