please generete a brief comment for the following function:def generateParenthesis(self, n: int) -> List[str]:
	def dfs(left, right, s):
		if len(s) == n * 2:
			res.append(s)
			return 

		if left < n:
			dfs(left + 1, right, s + '(')

		if right < left:
			dfs(left, right + 1, s + ')')

	res = []
	dfs(0, 0, '')
	return res