<record id="workcenter_line_gantt_production" model="ir.ui.view">

    <field name="name">mrp.production.work.order.gantt.production</field>

    <field name="model">mrp.workorder</field>

    <field name="arch" type="xml">

        <gantt date_stop="date_planned_finished" date_start="date_planned_start"         string="Operations" default_group_by="production_id">

        </gantt>

    </field>

</record>

<record id="mrp_workorder_view_gantt" model="ir.ui.view">

    <field name="name">mrp.workorder.view.gantt</field>

    <field name="model">mrp.workorder</field>

    <field name="arch" type="xml">

        <gantt date_stop="date_planned_finished" date_start="date_planned_start"         string="Operations" default_group_by="workcenter_id">

        </gantt>

    </field>

</record>

this is odoo code mrp_workorder_views.xml 

but not display in gantt chart, i what to do ?