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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 _start_refresh_timer(self):
 """Start the Vim timer. """

        if not self._timer:
            self._timer = self._vim.eval(
                "timer_start({}, 'EnTick', {{'repeat': -1}})"
                .format(REFRESH_TIMER)
            )