import type { FetchParameters } from './fetch';
/**
 * Generic utility function to set any header value in fetch parameters
 * @param headerName - The name of the header to set
 * @param headerValue - The value to set for the header
 * @param fetchParams - The fetch parameters [resource, options]
 * @param options - Additional options
 * @param options.throwOnExisting - If true, throws an error when the header already exists
 * @param options.errorMessage - Custom error message to use when header exists
 * @returns Modified fetch parameters with the header set
 */
export declare function setHeader<T extends string = string>(headerName: T, headerValue: string, [resource, options]: FetchParameters, { throwOnExisting, errorMessage, }?: {
    throwOnExisting?: boolean;
    errorMessage?: string;
}): FetchParameters;