public DocumentProcessingHandlerParameters setChainsModel(ChainsModel chainsModel) {
        this.chainsModel = chainsModel;
        return this;
    }
Returns the chains model, used to build call stacks.
@return the chains model, used to build call stacks.
docproc/src/main/java/com/yahoo/docproc/jdisc/DocumentProcessingHandlerParameters.java