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;
}