Set the graphite key prefixes

        :param dict conf: The configuration data

def _set_prefixes(self, conf):
        """Set the graphite key prefixes

        :param dict conf: The configuration data

        """
        if conf.get('legacy_namespace', 'y') in self.TRUE_VALUES:
            self.count_prefix = 'stats_counts'
            self.count_suffix = ''
            self.gauge_prefix = 'stats.gauges'
            self.timer_prefix = 'stats.timers'
            self.rate_prefix = 'stats'
            self.rate_suffix = ''
        else:
            global_prefix = conf.get('global_prefix', 'stats')
            self.count_prefix = '%s.%s' % (global_prefix,
                                           conf.get('prefix_counter',
                                                    'counters'))
            self.count_suffix = '.count'
            self.gauge_prefix = '%s.%s' % (global_prefix,
                                           conf.get('prefix_gauge', 'gauges'))
            self.timer_prefix = '%s.%s' % (global_prefix,
                                           conf.get('prefix_timer', 'timers'))
            self.rate_prefix = self.count_prefix
            self.rate_suffix = '.rate'