how can i use function value in Domain filter
<p>I am getting current login user id by following function</p>

<pre><code>    def _get_user_name(self, cr, uid, *args):
    user_obj = self.pool.get('res.users')
    user_value = user_obj.browse(cr, uid, uid)
    return user_value.id or False
</code></pre>

<p>and now i want to use its value in this field's Domain like ....</p>

<pre><code>    x_trainer_id = fields.Many2one('res.partner', string='Trainer',domain=[('user_id.id','=','get_user_name')])
</code></pre>

<p>How is it possible? I'll be very thankful....</p>