code: func (ds *DjangoSession) Insert(db XODB) error {
  	var err error
  
  	// if already exist, bail
  	if ds._exists {
  		return errors.New("insert failed: already exists")
  	}
  
  	// sql insert query, primary key must be provided
  	const sqlstr = `INSERT INTO public.django_session (` +
  		`session_key, session_data, expire_date` +
  		`) VALUES (` +
  		`$1, $2, $3` +
  		`)`
  
  	// run query
  	XOLog(sqlstr, ds.SessionKey, ds.SessionData, ds.ExpireDate)
  	err = db.QueryRow(sqlstr, ds.SessionKey, ds.SessionData, ds.ExpireDate).Scan(&ds.SessionKey)
  	if err != nil {
  		return err
  	}
  
  	// set existence
  	ds._exists = true
  
  	return nil
  }
docs: // Insert inserts the DjangoSession to the database.