code: def shrink_file(in_filepath, api_key=None, out_filepath=None):
      
      info = get_shrink_file_info(in_filepath, api_key, out_filepath)
      write_shrunk_file(info)
      return info
docs: Shrink png file and write it back to a new file
  
      The default file path replaces ".png" with ".tiny.png".
      returns api_info (including info['ouput']['filepath'])