code: public AutoComplete autoCompleteCommand(String prefix) {
          final Trie<CliValueType> possibilities = childCommands.subTrie(prefix).mapValues(CliValueType.COMMAND.<CliCommand>getMapper());
          return new AutoComplete(prefix, possibilities);
      }
docs: Auto complete the given prefix with child command possibilities.
  
  @param prefix Prefix to offer auto complete for.
  @return Auto complete for the child {@link CliCommand}s that starts with the given prefix. Case insensitive.