Python Code:-

class product_available_stock(models.Model):
_name = "product.available.stock"


product_name = fields.Many2one("product.template")
variants = fields.Many2one("product.attribute.value")


def state_id_change(self, cr, uid, ids, product_name):
    values = {'variants': False}

    if product_name:
        state = self.product_name.ids
        values['variants'] = state.variants.id

    return {'value': values}

XML Code:-

<group>
   <field name="product_name" on_change="state_id_change(product_name)"/>
   <field name="variants"/>
</group>

May I get any help on the above topic?