eiru_purchase_to_sale/views/template.xml

<openerp>
    <data>
        <template id="eiru_purchase_to_sale.assets_backend" name="purchase_to_sale_assets" inherit_id="eiru_assets.assets">
            <xpath expr="." position="inside">
                <script type="text/javascript" src="/eiru_purchase_to_sale/static/src/js/main.js"/>
                <!-- <script type="text/javascript" src="/eiru_purchase_to_sale/static/src/js/custom.js"/> -->
            </xpath>
        </template>
    </data>
</openerp>