export default abstract class MultiValueMap<K, V> extends Map<K, V[]> {
abstract add(key: K, value: V): void;
abstract addAll(key: K, values: V[]): void;
abstract addAll(values: MultiValueMap<K, V>): void;
containsKey(key: K): boolean;
addIfAbsent(key: K, value: V): void;
}