code: def init_app(self, app):
          
  
          for k, v in DEFAULT_SETTINGS.items():
              app.config.setdefault(k, v)
  
          if app.debug and not get_setting('FLASKS3_DEBUG', app):
              app.config['FLASKS3_ACTIVE'] = False
  
          if get_setting('FLASKS3_ACTIVE', app):
              app.jinja_env.globals['url_for'] = url_for
          if get_setting('FLASKS3_USE_CACHE_CONTROL', app) and app.config.get('FLASKS3_CACHE_CONTROL'):
              cache_control_header = get_setting('FLASKS3_CACHE_CONTROL', app)
              app.config['FLASKS3_HEADERS']['Cache-Control'] = cache_control_header
docs: An alternative way to pass your :class:`flask.Flask` application
          object to Flask-S3. :meth:`init_app` also takes care of some
          default `settings`_.
  
          :param app: the :class:`flask.Flask` application object.