anchor.diff:  ///  * [FilterChip], uses tags or descriptive words as a way to filter content.
   ///  * <https://material.google.com/components/chips.html>
   abstract class SelectableChipAttributes {
  +  // This class is intended to be used as an interface, and should not be
  +  // extended directly.
  +  factory SelectableChipAttributes._() => null;
  +
     /// Whether or not this chip is selected.
     ///
     /// If [onSelected] is not null, this value will be used to determine if the
  
positive.code: /// button for deleting the chip.
  ///
  /// Requires one of its ancestors to be a [Material] widget. The [label],
  /// [deleteIcon] and [border] arguments must not be null.
  ///
  /// ## Sample code
  ///
  
negative.code: ///    compact form.
  ///  * <https://material.google.com/components/chips.html>
  abstract class DeletableChipAttributes {
    // This class is intended to be used as an interface, and should not be
    // extended directly.
    factory DeletableChipAttributes._() => null;
  
    /// The icon displayed when [onDeleted] is set.
    ///
    /// Defaults to an [Icon] widget set to use [Icons.cancel].
  