import { Observable, UnaryFunction } from 'rxjs';
/**
 * Utility operator to ease debugging of observables.
 *
 * Example of usage:
 * ```
 * obs$.pipe(log('users'))
 * ```
 * @param info optional data. Usually helps to identify the logged stream
 */
export declare function log$<T>(info?: unknown, predicateFn?: (data?: T) => any): UnaryFunction<Observable<T | null | undefined>, Observable<T>>;