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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 child_level(self):
 """Return the child level given handled levels."""

        HANDLED_LEVELS = current_app.config.get('HANDLED_LEVELS')
        try:
            return HANDLED_LEVELS[HANDLED_LEVELS.index(self.level) - 1]
        except (IndexError, ValueError):
            return None