code: def get_items_stats(key, value):
          
          itemized_key = key.split(':')
          slab_id = itemized_key[1]
          metric = itemized_key[2]
  
          tags = ["slab:{}".format(slab_id)]
  
          return metric, tags, value
docs: Optional metric handler for 'items' stats
  
          key: "items:<slab_id>:<metric_name>" format
          value: return untouched
  
          Like all optional metric handlers returns metric, tags, value