>>>
class _SimpleNodeValidator {
  factory _SimpleNodeValidator.allowImages(UriPolicy uriPolicy) {
    return new _SimpleNodeValidator(uriPolicy,
        allowedElements: const ['IMG'],
        allowedAttributes: const [
      'IMG::align',
      'IMG::alt',
      'IMG::border',
      'IMG::height',
      'IMG::hspace',
      'IMG::ismap',
      'IMG::name',
      'IMG::usemap',
      'IMG::vspace',
      'IMG::width',
    ],
        allowedUriAttributes: const ['IMG::src',]);
  }
}
<<<
class _SimpleNodeValidator {
  factory _SimpleNodeValidator.allowImages(UriPolicy uriPolicy) {
    return new _SimpleNodeValidator(uriPolicy, allowedElements: const [
      'IMG'
    ], allowedAttributes: const [
      'IMG::align',
      'IMG::alt',
      'IMG::border',
      'IMG::height',
      'IMG::hspace',
      'IMG::ismap',
      'IMG::name',
      'IMG::usemap',
      'IMG::vspace',
      'IMG::width',
    ], allowedUriAttributes: const [
      'IMG::src',
    ]);
  }
}