docs: def process_tags(self, tag=None):
          """Process ID3 Tags for mp3 files."""
          if self.downloaded is False:
              raise serror("Track not downloaded, can't process tags..")
          filetype = magic.from_file(self.filepath, mime=True)
          if filetype != "audio/mpeg":
              raise serror("Cannot process tags for file type %s." % filetype)
  
          print("Processing tags for %s.." % self.filepath)
          if tag is None:
              tag = stag()
          tag.load_id3(self)
          tag.write_id3(self.filepath)