/**
 * Add up the given array of numbers, using the given function or key.
 *
 * @example
 * const users = [
 *   { age: 1, name: 'user1' },
 *   { age: 2, name: 'user2' },
 *   { age: 3, name: 'user3' },
 * ]
 * sumBy(users, user => user.age) // => 6
 * sumBy(users, 'age') // => 6
 */
export declare function sumBy<T extends Record<string, unknown>>(array: readonly T[], predicate: ((arg: T) => number) | {
    [K in keyof T]: T[K] extends number ? K : never;
}[keyof T]): number;
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