/**
 * The base implementation of `_.flatten` with support for restricting flattening.
 *
 * @private
 * @param {Array} array The array to flatten.
 * @param {number} depth The maximum recursion depth.
 * @param {boolean} [predicate=isFlattenable] The function invoked per iteration.
 * @param {boolean} [isStrict] Restrict to values that pass `predicate` checks.
 * @param {Array} [result=[]] The initial result value.
 * @returns {Array} Returns the new flattened array.
 */
export default function baseFlatten(array: any[], depth: number, predicate?: (value: any) => boolean, isStrict?: boolean): any[];