title: OpenERP : Multiple module overriding onchange function
body: <p>I need to override <code>onchange_partner_id</code> function present in sale.order but I'm working on a system that already have a module overriding this function.
  I tried to write my own <code>onchange_partner_id</code> with similar code :</p>
  
  <pre><code>def onchange_partner_id(self, cr, uid, ids, part):
      res = super(sale_order, self).onchange_partner_id(cr, uid, ids, part)
      // doing some stuff and adding it to res['value']['myfield']
  return res
  </code></pre>
  
  <p>But my function isn't read by OpenERP.
  So my question is, is it possible to have multiple function overriding the same function and if i's possible how do I proceed ?
  Thanks in advance</p>