code: def change_extension(self, filepath, new_extension):
          
          filename, ext = os.path.splitext(filepath)
          return '.'.join([filename, new_extension])
docs: Change final filename extension.
  
          Args:
              filepath (str): A file path (relative or absolute).
              new_extension (str): New extension name (without leading dot) to
                  apply.
  
          Returns:
              str: Filepath with new extension.