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

def get_slabs_stats(key, value):
        """
        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
        """
        slabbed_key = key.split(':')
        tags = []
        if len(slabbed_key) == 2:
            slab_id = slabbed_key[0]
            metric = slabbed_key[1]
            tags = ["slab:{}".format(slab_id)]
        else:
            metric = slabbed_key[0]

        return metric, tags, value