code: public List<ConfigElement> getNestedInstances(RegistryEntry re) throws ConfigMergeException {
          return getNestedInstances(re, new HashSet<RegistryEntry>());
      }
docs: Given a Pid and corresponding metatype registry entry, this finds all the ConfigElements with the parentPID specified in the registry entry
  and then all the children with given (factory) pid of those parent instances.
  
  @param pid (factory) pid of a registry entry.
  
  @return list of all the instances of the supplied (factory) pid that are nested inside a parent of the parentPID from the registry entry.
  @throws ConfigMergeException