export declare class TfIdfIndex {
    private documents;
    private df;
    private idf;
    private documentCount;
    addDocument(id: number, tokens: string[]): void;
    removeDocument(id: number): void;
    query(tokens: string[], topK?: number): Array<{
        id: number;
        score: number;
    }>;
    getDocumentCount(): number;
    getIdf(): ReadonlyMap<string, number>;
    private recomputeIdfForTerms;
}
