code: private String getExtends(String pid) {
          RegistryEntry re = getRegistryEntry(pid);
          return re == null ? null : re.getExtends();
      }
docs: Find the "super" PID from the <code>ibm:extends</code> attribute of the OCD for <code>pid</code>.
  
  @param pid must never be null
  @return the super PID or <code>null</code> if no <code>ibm:extends</code> attribute could be found