Given a message ID, finds the media this message contained and
           downloads it.

async def download_media_by_id(self, media_id):
        """Given a message ID, finds the media this message contained and
           downloads it.
        """
        try:
            msg = self.found_media[int(media_id)]
        except (ValueError, KeyError):
            # ValueError when parsing, KeyError when accessing dictionary
            print('Invalid media ID given or message not found!')
            return

        print('Downloading media to usermedia/...')
        os.makedirs('usermedia', exist_ok=True)
        output = await self.download_media(
            msg.media,
            file='usermedia/',
            progress_callback=self.download_progress_callback
        )
        print('Media downloaded to {}!'.format(output))