code: func (cmd *CancelAllocationCommand) Source() (interface{}, error) {
  	source := make(map[string]interface{})
  	source["index"] = cmd.index
  	source["shard"] = cmd.shardId
  	source["node"] = cmd.node
  	source["allow_primary"] = cmd.allowPrimary
  	return source, nil
  }
docs: // Source generates the (inner) JSON to be used when serializing the command.