code: func (gss *genericSubStore) CreateSub(sub *spb.SubState) error {
  	gss.Lock()
  	err := gss.createSub(sub)
  	gss.Unlock()
  	return err
  }
docs: // CreateSub records a new subscription represented by SubState. On success,
  // it records the subscription's ID in SubState.ID. This ID is to be used
  // by the other SubStore methods.