code: func (s *StandardChannel) ProcessConfigMsg(env *cb.Envelope) (config *cb.Envelope, configSeq uint64, err error) {
  	logger.Debugf("Processing config message for channel %s", s.support.ChainID())
  
  	configEnvelope := &cb.ConfigEnvelope{}
  	_, err = utils.UnmarshalEnvelopeOfType(env, cb.HeaderType_CONFIG, configEnvelope)
  	if err != nil {
  		return
  	}
  
  	return s.ProcessConfigUpdateMsg(configEnvelope.LastUpdate)
  }
docs: // ProcessConfigMsg takes an envelope of type `HeaderType_CONFIG`, unpacks the `ConfigEnvelope` from it
  // extracts the `ConfigUpdate` from `LastUpdate` field, and calls `ProcessConfigUpdateMsg` on it.