Given a string s represents the serialization of a nested list, implement a parser to deserialize it and return the deserialized NestedInteger. Each element is either an integer or a list whose elements may also be integers or other lists. Example 1: Input: s = "324" Output: 324 Explanation: You should return a NestedInteger object which contains a single integer 324. Example 2: Input: s = "[123,[456,[789]]]" Output: [123,[456,[789]]] Explanation: Return a NestedInteger object containing a nested list with 2 elements: 1. An integer containing value 123. 2. A nested list containing two elements: i. An integer containing value 456. ii. A nested list with one element: a. An integer containing value 789 Constraints: 1 <= s.length <= 5 * 104 s consists of digits, square brackets "[]", negative sign '-', and commas ','. s is the serialization of valid NestedInteger.