export declare const DEFAULT_MASK_HEADERS: string[];
export interface ExtractHeadersOptions {
    replacement?: string;
    multiValue?: boolean;
}
export declare function extractHeaders(headers: unknown, maskHeaders: Iterable<string>, options: ExtractHeadersOptions & {
    multiValue: true;
}): Record<string, string | string[]>;
export declare function extractHeaders(headers: unknown, maskHeaders: Iterable<string>, options?: ExtractHeadersOptions): Record<string, string>;
export declare function formatHeaderValue(value: unknown): string;