/**
 * Extracts a human-readable error message from an unknown error value.
 * Safely handles various error formats including Error objects, objects with message properties,
 * and other unknown values.
 *
 * @param error - The error value to extract a message from. Can be any type.
 * @returns The extracted error message string, or 'unknown' if no message could be extracted.
 *
 * @example
 * ```ts
 * getErrorMessage(new Error('Something went wrong')); // 'Something went wrong'
 * getErrorMessage({ message: 'Custom error' }); // 'Custom error'
 * getErrorMessage(null); // 'unknown'
 * ```
 */
export declare function getErrorMessage(error: unknown): string;
/**
 * Formats JSON data with custom styling rules for map-style configurations.
 * Applies special formatting for certain paths (like bounds, layers, filters, paint, layout)
 * to keep them on a single line while expanding other nested structures.
 *
 * @param inputData - The data to format as styled JSON.
 * @returns A formatted JSON string with custom indentation and line breaks.
 *
 * @example
 * ```ts
 * prettyStyleJSON({ name: 'test', bounds: [0, 0, 1, 1] });
 * // Returns formatted JSON with bounds on a single line
 * ```
 */
export declare function prettyStyleJSON(inputData: unknown): string;