code: func (c *Cluster) Split(regionID, newRegionID uint64, key []byte, peerIDs []uint64, leaderPeerID uint64) {
  	c.SplitRaw(regionID, newRegionID, NewMvccKey(key), peerIDs, leaderPeerID)
  }
docs: // Split splits a Region at the key (encoded) and creates new Region.