private static RankingConstantsConfig.Constant.Builder toConfig(DistributableConstant constant) {
        return new RankingConstantsConfig.Constant.Builder()
                .name(constant.getName())
                .fileref(constant.getFileReference())
                .type(constant.getType());
    }
Returns a read-only map of the constants in this indexed by name.
config-model/src/main/java/com/yahoo/schema/derived/FileDistributedConstants.java