docs: def Get(self):
      """Return a GrrMessage instance from the transaction log or None."""
      try:
        value, reg_type = winreg.QueryValueEx(_GetServiceKey(), "Transaction")
      except OSError:
        return
  
      if reg_type != winreg.REG_BINARY:
        return
  
      try:
        return rdf_flows.GrrMessage.FromSerializedString(value)
      except message.Error:
        return