enum AttributeScope {
  INLINE, // refer to https://quilljs.com/docs/formats/#inline
  BLOCK, // refer to https://quilljs.com/docs/formats/#block
  EMBEDS, // refer to https://quilljs.com/docs/formats/#embeds
}

class Attribute<T> {
  final String key;
  final AttributeScope scope;

  Attribute(this.key, this.scope);
}

class BoldAttribute extends Attribute<bool> {
  BoldAttribute() : super('bold', AttributeScope.INLINE);
}

class ItalicAttribute extends Attribute<bool> {
  ItalicAttribute() : super('italic', AttributeScope.INLINE);
}

class UnderlineAttribute extends Attribute<bool> {
  UnderlineAttribute() : super('underline', AttributeScope.INLINE);
}

class StrikeThroughAttribute extends Attribute<bool> {
  StrikeThroughAttribute() : super('strike', AttributeScope.INLINE);
}