/**
 * Principal curves
 */
export default class PrincipalCurve {
    _l: any;
    /**
     * Fit model.
     * @param {Array<Array<number>>} x Training data
     */
    fit(x: Array<Array<number>>): void;
    _bending(x: any): void;
    /**
     * Returns reduced datas.
     * @returns {Array<Array<number>>} Predicted values
     */
    predict(): Array<Array<number>>;
}