export declare const ALTERNATE_RENDER_TARGET_IDS: readonly ['email', 'mjml', 'plain-text'];
export type AlternateRenderTargetId = (typeof ALTERNATE_RENDER_TARGET_IDS)[number];
export declare function isAlternateRenderTargetId(value: string): value is AlternateRenderTargetId;
export declare function parseAlternateRenderTargets(value?: string): AlternateRenderTargetId[];
export declare function formatAlternateRenderTargets(targets: readonly AlternateRenderTargetId[]): string;