/**
 * Calculates the average of an array of numbers.
 *
 * @param {number[]} nums - The array of numbers to calculate the average of.
 * @returns {number} The average of the numbers in the array.
 * @throws {Error} If the input is not a non-empty array of numbers.
 * @throws {Error} If any element in the array is not a valid number.
 */
export declare function getAverage(arr: number[]): number;