def METHOD_NAME(self, stream):
    super().METHOD_NAME(stream)
    if self.reference is None:
        alignment = next(self)
        self.reference, chromosome = alignment.sequences[0].id.split(".", 1)
        self.rewind()
    else:
        self.targets[0].id = "%s.%s" % (self.reference, self.targets[0].id)