import { BaseEstimator } from "./estimator";
import type { FeatureData, FeatureDataKind } from '../data';
/**
 * Base class for feature transformers (scalers, encoders, decomposition,
 * feature selection, ...). `y` is accepted for pipeline compatibility and
 * used only by supervised transformers.
 */
export declare abstract class TransformerBase<TInput extends FeatureData = number[][], TOutput extends FeatureData = number[][]> extends BaseEstimator {
    /** Runtime companion to the generic input type (which is erased in JS). */
    readonly acceptedInputKinds: readonly FeatureDataKind[];
    abstract fit(X: TInput, y?: number[]): void;
    abstract transform(X: TInput): TOutput;
    fitTransform(X: TInput, y?: number[]): TOutput;
    /** Optional capability: invert the transformation where well-defined. */
    inverseTransform?(X: TOutput): TInput;
}