function prepare_attributes (Optional[Hash[String, Any]] $attributes) {
  $attributes.lest || { {} }.filter |$items| { $items[1] != undef }.reduce({})
    |Hash $memo,
     Variant[Tuple[Enum[before, consume, export, notify, require, subscribe],
                   Array[Variant[Type[Resource], Pattern[/\A[A-Z][a-z]*(?:::[A-Z][a-z]*)*\[[^\[\]]+\]\Z/]]]],
             Tuple[String, Data]] $items| {
    if $items =~ Tuple[String, Data] {
      $memo + Hash.new($items)
    }
    else {
      $resources = $items[1].map |$item| {
        case $item {
          Resource: {
            $item
          }
          /\A([A-Z][a-z]*(?:::[A-Z][a-z]*)*)\[([^\[\]]+)\]\Z/: {
            Resource[$1][$2]
          }
        }
      }
      $memo + { $items[0] => $resources }
    }
  }
}