code: function (cb3) {
          blockChain.getDetails(uncle.hash(), function (err, blockInfo) {
            // TODO: remove uncles from BC
            if (blockInfo && blockInfo.isUncle) {
              cb3(err || 'uncle already included')
            } else {
              cb3()
            }
          })
        }
docs: check to make sure the uncle is not already in the blockchain