cdm/src/main/java/thredds/client/catalog/builder/DatasetBuilder.java
public Dataset copyDataset(DatasetNode parent) {
    return new Dataset(parent, name, flds, accessBuilders, datasetBuilders);
  }
public Dataset copyDataset(DatasetNode parent) {
    return new Dataset(parent, name, flds, accessBuilders, datasetBuilders);
  }
make an immutable copy without changin DatasetBuilder