Image you are buliding a compiler.
Before running any code, the compiler must check
that the parentheses in the program are balanced.

Every opening bracket must have a corresponding closing bracket.
We can approximate this using strings.

Given a string containing just the characters '(', ')', '{', '}', '[' and ']',
determine if the input string is valid.

An input string is valid if:

* open brackets are closed by the same type of brackets.
* open brackets are closed in the correct order.
* Note that an empty string is also considered valid.

Example:

Input: "((()))"
Output: True

Input: "[()]{}"
Output: True

Input: "({[)]"
Output: False


```python
class Solution:
  def isValid(self, s):
    # TODO::

assert False, Solution.isValid("()(){(())")
assert True, Solution.isValid("")
assert True, Solution.isValid("([{}])()")
```