/**
 * Checks if `value` is a plain object, that is, an object created by the
 * `Object` constructor or one with a `[[Prototype]]` of `null`.
 *
 * @param value The value to check.
 * @return Returns `true` if `value` is a plain object, else `false`.
 * @example
 *
 * function Foo() {
 *   this.a = 1
 * }
 *
 * isPlainObject(new Foo)
 * // => false
 *
 * isPlainObject([1, 2, 3])
 * // => false
 *
 * isPlainObject({ 'x': 0, 'y': 0 })
 * // => true
 *
 * isPlainObject(Object.create(null))
 * // => true
 */
export declare const isPlainObject: (value: unknown) => value is object;