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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 unassign(pid_type, pid_value):
 """Unassign persistent identifier."""

    from .models import PersistentIdentifier

    obj = PersistentIdentifier.get(pid_type, pid_value)
    obj.unassign()
    db.session.commit()
    click.echo(obj.status)