code: func (is *identityMapperImpl) validateIdentities(isSuspected api.PeerSuspector) []*storedIdentity {
  	now := time.Now()
  	usageTh := GetIdentityUsageThreshold()
  	is.RLock()
  	defer is.RUnlock()
  	var revokedIdentities []*storedIdentity
  	for pkiID, storedIdentity := range is.pkiID2Cert {
  		if pkiID != is.selfPKIID && storedIdentity.fetchLastAccessTime().Add(usageTh).Before(now) {
  			revokedIdentities = append(revokedIdentities, storedIdentity)
  			continue
  		}
  		if !isSuspected(storedIdentity.peerIdentity) {
  			continue
  		}
  		if err := is.mcs.ValidateIdentity(storedIdentity.fetchIdentity()); err != nil {
  			revokedIdentities = append(revokedIdentities, storedIdentity)
  		}
  	}
  	return revokedIdentities
  }
docs: // validateIdentities returns a list of identities that have been revoked, expired or haven't been
  // used for a long time