code: func (c *codecPDClient) GetRegionByID(ctx context.Context, regionID uint64) (*metapb.Region, *metapb.Peer, error) {
  	region, peer, err := c.Client.GetRegionByID(ctx, regionID)
  	return processRegionResult(region, peer, err)
  }
docs: // GetRegionByID encodes the key before send requests to pd-server and decodes the
  // returned StartKey && EndKey from pd-server.