cdm/src/main/java/ucar/nc2/ft/point/standard/NestedTable.java
private boolean isExtra(Variable v) {
    return v != null && extras != null && extras.contains(v);
  }
private boolean isExtra(Variable v) {
    return v != null && extras != null && extras.contains(v);
  }
Has v already been added to the set of extra variables?