code: def delete(self, model, commit=True):
          
          self.is_instance(model)
          db.session.delete(model)
          if commit:
              db.session.commit()
  
          return model
docs: Delete
          Puts model for deletion into unit of work and optionall commits
          transaction
  
          :param model:           object, model to delete
          :param commit:          bool, commit?
          :return:                object, deleted model