/**
 * Iterates through a collection to find a matching item and returns the index.
 *
 * @param needle The item to search for
 * @param haystack The collection to search
 * @param keyFields The fields used to indicate a match
 * @returns Index of `needle` in `haystack`, otherwise -1 if not found.
 */
export declare function findIndexByFields<T>(needle: T, haystack: T[], keyFields: (keyof T)[]): number;