inheritance - Odoo 8 - Add button in invoice supplier form -

i try add documentation says , when update module doesn't work.

<record id="some_example_id" model="ir.ui.view">      <field name="name">example.name</field>      <field name="model">account.invoice</field>      <field name="inherit_id" ref="account.invoice_supplier_form" />      <field name="arch" type="xml">          <data>              <button name="invoice_cancel" position="after">                  <button name="test_button" states="draft,proforma2,open" string="test" groups="base.group_no_one" class="oe_highlight"/>              </button>          </data>      </field>  </record>  

exactly here

your code seems me. may try following tips.

• make sure xml file name given in manifest file.
• active debugger mode.
• temporary remove groups="base.group_no_one" button , upgrade module.

just note:

your button call workflow because didn't give type attribute button. if want call python function directly need add attribute in button like

type="object"