def update(self, vts):
    """Mark a changed or invalidated VersionedTargetSet as successfully processed."""
    for vt in vts.versioned_targets:
      vt.ensure_legal()
      if not vt.valid:
        self._invalidator.update(vt.cache_key)
        vt.valid = True
        self._artifact_write_callback(vt)
    if not vts.valid:
      vts.ensure_legal()
      self._invalidator.update(vts.cache_key)
      vts.valid = True
      self._artifact_write_callback(vts)
Mark a changed or invalidated VersionedTargetSet as successfully processed.