code: func (c *Cluster) SplitRaw(regionID, newRegionID uint64, rawKey []byte, peerIDs []uint64, leaderPeerID uint64) {
  	c.Lock()
  	defer c.Unlock()
  
  	newRegion := c.regions[regionID].split(newRegionID, rawKey, peerIDs, leaderPeerID)
  	c.regions[newRegionID] = newRegion
  }
docs: // SplitRaw splits a Region at the key (not encoded) and creates new Region.