code: func (a *Authenticator) PurgeCredentialsCache() error {
  	a.lock.Lock()
  	defer a.lock.Unlock()
  	if err := a.ensureInitialized(); err != nil {
  		return err
  	}
  	return a.purgeCredentialsCacheLocked()
  }
docs: // PurgeCredentialsCache removes cached tokens.
  //
  // Does not revoke them!