code: function isOneOrMore(commands, iterator) {
      var list = commands.filter(iterator);
  
      if (list.length === 1) {
        return list[0];
      } else if (list.length > 1) {
        return new Error(util.format('There are %d options for "%s": %s',
          list.length, cmd, list.join(', ')));
      }
  
      return false;
    }
docs: Determine how many commands match the iterator. Return one if command,