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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 get_alert(self, stat, header=""):
 """Manage limits of the folder list."""

        if not isinstance(stat['size'], numbers.Number):
            ret = 'DEFAULT'
        else:
            ret = 'OK'

            if stat['critical'] is not None and \
               stat['size'] > int(stat['critical']) * 1000000:
                ret = 'CRITICAL'
            elif stat['warning'] is not None and \
                    stat['size'] > int(stat['warning']) * 1000000:
                ret = 'WARNING'
            elif stat['careful'] is not None and \
                    stat['size'] > int(stat['careful']) * 1000000:
                ret = 'CAREFUL'

        # Get stat name
        stat_name = self.get_stat_name(header=header)

        # Manage threshold
        self.manage_threshold(stat_name, ret)

        # Manage action
        self.manage_action(stat_name,
                           ret.lower(),
                           header,
                           stat[self.get_key()])

        return ret