input: def str_to_lower(input_str: str) -> str:
      """Convert the given string to its lowercase version.
  
      >>> str_to_lower("Hello World")
      'hello world'
      >>> str_to_lower("This IS a TEST")
      'this is a test'
      >>> str_to_lower("PYTHON")
      'python'
      """
      new_str = ''.join(char.lower() for char in input_str)
      return new_str
output:     new_str = ''.join(char.lower() for char in input_str)
      return new_str