export interface FragmentIdGenerator {
    /**
     * Called to generate the next id.
     *
     * Subsequent calls must return values that have not been returned before.
     *
     * @param fragmentToSources A readonly mapping of currently known fragment ids to sets of source ids that contain these fragments.
     */
    generate(fragmentToSources: ReadonlyMap<string, ReadonlySet<string>>): string;
}
/**
 * A fragment id generator that yields incrementing base 62 encoded numeric ids.
 */
export declare class Base62FragmentIdGenerator implements FragmentIdGenerator {
    #private;
    generate(): string;
}