docs: def save(self, path):
          """Save the track"""
          name = Track.filename(self.name)
          with open(os.path.join(path, name), 'wb') as fd:
              fd.write(struct.pack('>I', len(self.keys)))
              for k in self.keys:
                  fd.write(struct.pack('>ifb', k.row, k.value, k.kind))