import { PipeTransform } from "@angular/core";
import { AbstractControl, FormGroup } from "@angular/forms";
import { Observable } from "rxjs";
import * as i0 from "@angular/core";
export declare class FormHeaderIconPipePipe implements PipeTransform {
    static readonly ERROR_ICON_DEFAULT = "status_critical";
    transform(form: FormGroup | AbstractControl | null, defaultIcon: string, errorIcon?: string): Observable<string | null>;
    static ɵfac: i0.ɵɵFactoryDeclaration<FormHeaderIconPipePipe, never>;
    static ɵpipe: i0.ɵɵPipeDeclaration<FormHeaderIconPipePipe, "nuiFormHeaderIconPipe", false>;
}