How to use the openupgradelib.openupgrade function in openupgradelib

@openupgrade.migrate(use_env=True)
def migrate(env, version):
    """ Completamos fecha a nuevo campo:
    * tomando de payment_date si está seteado
    * tomando de confirmation_date si ya se paso a proceso de firma pero no
    tenemos payment_date
    """
    cr = env.cr

    cr.execute("""
        UPDATE account_payment_group set to_signature_date=payment_date
        WHERE payment_date is not null
    """)

    cr.execute("""
        UPDATE account_payment_group set to_signature_date=confirmation_date