anchor.diff:      final context = VerificationContext();
       if (d.key.present) {
         context.handle(_keyMeta, key.isAcceptableValue(d.key.value, _keyMeta));
  -    } else if (key.isRequired && isInserting) {
  +    } else if (isInserting) {
         context.missing(_keyMeta);
       }
       if (d.value.present) {
         context.handle(
             _valueMeta, value.isAcceptableValue(d.value.value, _valueMeta));
  -    } else if (value.isRequired && isInserting) {
  +    } else if (isInserting) {
         context.missing(_valueMeta);
       }
       return context;
  
positive.code:     );
    }
    factory KeyValue.fromJson(Map<String, dynamic> json,
        {ValueSerializer serializer = const ValueSerializer.defaults()}) {
      return KeyValue(
        key: serializer.fromJson<String>(json['key']),
        value: serializer.fromJson<String>(json['value']),
      );
    }
    @override
    Map<String, dynamic> toJson(
        {ValueSerializer serializer = const ValueSerializer.defaults()}) {
      return <String, dynamic>{
        'key': serializer.toJson<String>(key),
        'value': serializer.toJson<String>(value),
  
negative.code:   $KeyValuesTable _keyValues;
    $KeyValuesTable get keyValues => _keyValues ??= $KeyValuesTable(this);
    @override
    Iterable<TableInfo> get allTables => allSchemaEntities.whereType<TableInfo>();
    @override
    List<DatabaseSchemaEntity> get allSchemaEntities => [keyValues];
  }
  