Write a Python function that checks whether a provided string is a valid IPv4 address or not. The function should take a single argument, which is the input string to be checked, and return a Boolean value indicating whether the input string is a valid IPv4 address or not. The input string should consist of four integers separated by periods, and each integer should fall between 0 and 255, inclusive. If the input string meets these criteria, the function should return True; otherwise, it should return False.
This prompt doesn't seem malicious.