input: 
  from typing import List
  
  def make_string_lowercase(input_string: str) -> str:
      """ Converts all characters of a given string to lowercase.
      
      >>> make_string_lowercase("HELLO")
      'hello'
      >>> make_string_lowercase("WoRlD")
      'world'
      """
      return input_string.lower()
  
output:     return input_string.lower()