title: openerp: Set default value for one2many field
body: <p>I need to set default value for one2many field. I tried it with a function in _defaults but my function doesn't get called.</p>
  
  <p>Here is my code:</p>
  
  <p>Field:</p>
  
  <pre><code>'tax_invoice_line_ids': fields.one2many('account.tax.line', 'tax_id', 'Tax Invoice', domain=[('apply_on','=','invoice')]),
  </code></pre>
  
  <p>_defaults:</p>
  
  <pre><code>_defaults = {
      'tax_invoice_line_ids': _invoice_line_default,
      }
  </code></pre>
  
  <p>_invoice_line_default:</p>
  
  <pre><code>def _invoice_line_default(self, cr, uid, context=None):
      print "\n\ncame here..........................................."
      return True
  </code></pre>
  
  <p>am i missing something?</p>
  
  <p>Thanx in advance.</p>