docs: def delete_instance(model, instance_id, _commit=True):
      """Delete instance.
  
      :param model: a string, model name in rio.models.
      :param instance_id: integer, instance id.
      :param _commit: control whether commit data to database or not. Default True.
      """
      try:
          model = get_model(model)
      except ImportError:
          return
  
      instance = model.query.get(instance_id)
      if not instance:
          return
  
      db.session.delete(instance)
      try:
          if _commit:
              db.session.commit()
          else:
              db.session.flush()
      except Exception as exception:
          db.session.rollback()
          raise exception