实现函数 ToLowerCase()，该函数接收一个字符串参数 str，并将该字符串中的大写字母转换成小写字母，之后返回新的字符串。

 

示例 1：

输入: "Hello"
输出: "hello"

示例 2：

输入: "here"
输出: "here"

示例 3：

输入: "LOVELY"
输出: "lovely"

一个一个的比着换，狠不狠。

class Solution:def toLowerCase(self, str: str) -> str:str=str.replace("A","a").replace("B","b").replace("C","c").replace("D","d").replace("E","e").replace("F","f").replace("G","g").replace("H","h").replace("I","i").replace("J","j").replace("K","k").replace("L","l").replace("M","m").replace("N","n").replace("O","o").replace("P","p").replace("Q","q").replace("R","r").replace("S","s").replace("T","t").replace("U","u").replace("V","v").replace("W","w").replace("X","x").replace("Y","y").replace("Z","z")return str