docs: def _check_slowlog(self, instance, custom_tags):
          """Retrieve length and entries from Redis' SLOWLOG
  
          This will parse through all entries of the SLOWLOG and select ones
          within the time range between the last seen entries and now
  
          """
          conn = self._get_conn(instance)
  
          tags = self._get_tags(custom_tags, instance)
  
          if not instance.get(MAX_SLOW_ENTRIES_KEY):
              try:
                  max_slow_entries = int(conn.config_get(MAX_SLOW_ENTRIES_KEY)[MAX_SLOW_ENTRIES_KEY])
                  if max_slow_entries > DEFAULT_MAX_SLOW_ENTRIES:
                      self.warning(
                          "Redis {0} is higher than {1}. Defaulting to {1}. "
                          "If you need a higher value, please set {0} in your check config".format(
                              MAX_SLOW_ENTRIES_KEY, DEFAULT_MAX_SLOW_ENTRIES
                          )
                      )
                      max_slow_entries = DEFAULT_MAX_SLOW_ENTRIES
              # No config on AWS Elasticache
              except redis.ResponseError:
                  max_slow_entries = DEFAULT_MAX_SLOW_ENTRIES
          else:
              max_slow_entries = int(instance.get(MAX_SLOW_ENTRIES_KEY))
  
          # Generate a unique id for this instance to be persisted across runs
          ts_key = self._generate_instance_key(instance)
  
          # Get all slowlog entries
  
          slowlogs = conn.slowlog_get(max_slow_entries)
  
          # Find slowlog entries between last timestamp and now using start_time
          slowlogs = [s for s in slowlogs if s['start_time'] > self.last_timestamp_seen[ts_key]]
  
          max_ts = 0
          # Slowlog entry looks like:
          #  {'command': 'LPOP somekey',
          #   'duration': 11238,
          #   'id': 496L,
          #   'start_time': 1422529869}
          for slowlog in slowlogs:
              if slowlog['start_time'] > max_ts:
                  max_ts = slowlog['start_time']
  
              slowlog_tags = list(tags)
              command = slowlog['command'].split()
              # When the "Garantia Data" custom Redis is used, redis-py returns
              # an empty `command` field
              # FIXME when https://github.com/andymccurdy/redis-py/pull/622 is released in redis-py
              if command:
                  slowlog_tags.append('command:{}'.format(ensure_unicode(command[0])))
  
              value = slowlog['duration']
              self.histogram('redis.slowlog.micros', value, tags=slowlog_tags)
  
          self.last_timestamp_seen[ts_key] = max_ts