Write a Python function to reverse a string.

You can reverse a string in Python using slicing, the reversed() function, or a loop. Here’s a simple implementation using slicing:

def reverse_string(s: str) -> str:
    return s[::-1]

This returns a new string that is the reverse of the input. For example, reverse_string('hello') returns 'olleh'. The slicing method is concise and runs in O(n) time, where n is the length of the string.