import type { Plugin } from 'postcss';
/**
 * Transforms a style sheet into atomic rules.
 * When passing a `callback` option it will callback with created class names.
 *
 * Preconditions:
 *
 * 1. No nested rules allowed - normalize them with the `parent-orphaned-pseudos` and `nested` plugins first.
 *
 * @throws Throws an error if `opts.classHashPrefix` contains invalid css class/id characters
 */
export declare const flattenMultipleSelectors: () => Plugin;