/**
 * (Private, not exported from the package) A stable string key for a value, so that array
 * membership can be decided by value instead of by reference.
 *
 * Python cannot hash a list or a dict at all, so a reference comparison could not have been
 * ported to all three languages. Comparing by value also means `arrDifference([[1]], [[1]])`
 * answers the same way everywhere.
 */
export declare function comparableKey(value: any): string;