code: def collect_sound_streams(self):
          
          rc = []
          current_stream = None
          # looking in all containers for frames
          for tag in self.all_tags_of_type((TagSoundStreamHead, TagSoundStreamBlock)):
              if isinstance(tag, TagSoundStreamHead):
                  # we have a new stream
                  current_stream = [ tag ]
                  rc.append(current_stream)
              if isinstance(tag, TagSoundStreamBlock):
                  # we have a frame for the current stream
                  current_stream.append(tag)
          return rc
docs: Return a list of sound streams in this timeline and its children.
          The streams are returned in order with respect to the timeline.
  
          A stream is returned as a list: the first element is the tag
          which introduced that stream; other elements are the tags
          which made up the stream body (if any).