contract/agreement_sale/views/agreement.xml

<?xml version="1.0"?>
<!--
  © 2017 Akretion (Alexis de Lattre <alexis.delattre@akretion.com>)
  License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
-->

<odoo>


<record id="agreement_form" model="ir.ui.view">
    <field name="name">agreement.form</field>
    <field name="model">agreement</field>
    <field name="inherit_id" ref="agreement_account.agreement_form"/>
    <field name="arch" type="xml">
        <group name="in_invoices" position="after">
            <group name="sale_orders" string="Sales Orders" attrs="{'invisible': [('agreement_type', '!=', 'sale')]}">
                <field name="sale_ids" nolabel="1"/>
            </group>
        </group>
    </field>
</record>


</odoo>