code: func (dct *DjangoContentType) Update(db XODB) error {
  	var err error
  
  	// if doesn't exist, bail
  	if !dct._exists {
  		return errors.New("update failed: does not exist")
  	}
  
  	// if deleted, bail
  	if dct._deleted {
  		return errors.New("update failed: marked for deletion")
  	}
  
  	// sql query
  	const sqlstr = `UPDATE public.django_content_type SET (` +
  		`app_label, model` +
  		`) = ( ` +
  		`$1, $2` +
  		`) WHERE id = $3`
  
  	// run query
  	XOLog(sqlstr, dct.AppLabel, dct.Model, dct.ID)
  	_, err = db.Exec(sqlstr, dct.AppLabel, dct.Model, dct.ID)
  	return err
  }
docs: // Update updates the DjangoContentType in the database.