def METHOD_NAME(self):
    super().METHOD_NAME()
    for move in self:
        if move.split_payment:
            if move.is_purchase_document():
                continue
            move.amount_sp = move.amount_tax
            move.amount_tax = 0.0
            move.amount_total = move.amount_untaxed
            move._compute_split_payments()
        else:
            move.amount_sp = 0.0