cdm/src/main/java/ucar/nc2/Variable.java
public Group getParentGroup() {
    Group g = super.getParentGroup();
    if (g == null) {
      g = ncfile.getRootGroup();
      super.setParentGroup(g);
    }

    assert g != null;
    return g;
  }
public Group getParentGroup() {
    Group g = super.getParentGroup();
    if (g == null) {
      g = ncfile.getRootGroup();
      super.setParentGroup(g);
    }

    assert g != null;
    return g;
  }
Get the parent group.

@return group of this variable; if null return rootgroup