title: How to call a method in odoo 7?
body: <p>I've created a method and I was using field function to call the method. But, the method never executes.<br>
  here is my code :</p>
  
  <pre><code>def _get_data_from_puchase_order(self, cr, ids, field, arg, context=None):
      print "SUCCESS"
      print ":::::::::::::::::"
      result = {}
      for row in self.browse(cr, uid, ids):
          print row
          print "::::::::::::"
  
  _columns = {
          "data_purchase_product" : fields.function(_get_data_from_puchase_order, method=True, string='origin', type='char', strore=False)
      }
  </code></pre>
  
  <p>i was add :</p>
  
  <pre><code>for data in self.pool.get('purchase.order').browse(cr, uid, ids):
      print data.name
      print "++++++++++++++++++"
  </code></pre>
  
  <p>and i got error :</p>
  
  <pre><code>MissingError: ('MissingError', u'One of the documents you are trying to access has been deleted, please try again after refreshing.')
  </code></pre>