code: func (s *CertFileUserStore) Store(user *msp.UserData) error {
  	key := storeKeyFromUserIdentifier(msp.IdentityIdentifier{MSPID: user.MSPID, ID: user.ID})
  	return s.store.Store(key, user.EnrollmentCertificate)
  }
docs: // Store stores a User into store