anchor.diff:            PackageVersionTags.isLegacy,
           ],
         );
  -
  -  /// Pre-populates the predicate with the default tags for all package listings
  -  /// (e.g. "My packages").
  -  factory TagsPredicate.allPackages() => TagsPredicate();
   
     bool get isEmpty => _values.isEmpty;
     bool get isNotEmpty => _values.isNotEmpty;
  
positive.code: /// Filter conditions on tags.
  class TagsPredicate {
    /// tag -> {true = required | false = prohibited}
    final _values = <String?, bool>{};
  
    TagsPredicate({List<String>? requiredTags, List<String>? prohibitedTags}) {
      requiredTags?.forEach((tag) => _values[tag] = true);
  
negative.code: 
    String? get sdk {
      final values = tagsPredicate._values.entries
          .where((e) => e.key.startsWith('sdk:') && e.value == true)
          .map((e) => e.key.split(':')[1]);
      return values.isEmpty ? null : values.first;
    }
  
  