cdm/src/main/java/ucar/nc2/iosp/hdf5/H5header.java
boolean isChildOf(H5Group that) {
      if (parent == null) return false;
      if (parent == that) return true;
      return parent.isChildOf(that);
    }
boolean isChildOf(H5Group that) {
      if (parent == null) return false;
      if (parent == that) return true;
      return parent.isChildOf(that);
    }
is this a child of that ?