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export class DefaultMap<K, V> extends Map<K, V> { constructor( private getDefaultValue: (key: K) => V, entries?: readonly (readonly [K, V])[] | null, ) { super(entries); } get = (key: K): V => { if (!this.has(key)) { this.set(key, this.getDefaultValue(key)); } /* eslint-disable @typescript-eslint/no-non-null-assertion */ return super.get(key)!; }; }