function isNull(value) {
    return value === null;
  }
Checks if `value` is `null`.

@static
@memberOf _
@category Objects
@param {*} value The value to check.
@returns {boolean} Returns `true` if the `value` is `null`, else `false`.
@example

_.isNull(null);
// => true

_.isNull(undefined);
// => false