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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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