title: XML context default One2many in odoo9
body: <p>I have a problem with this xml specification (odoo 9):</p>
  
  <blockquote>
    <p>the var "groups_ref" is a Many2many relation with res.groups.</p>
  </blockquote>
  
  <pre><code>&lt;record id="some_id" model="ir.actions.act_window"&gt;
      ....
      &lt;field name="context"&gt;{'groups_ref': self.env.ref('security.basic_user')}&lt;/field&gt;
      ....
  &lt;/record&gt;
  </code></pre>
  
  <blockquote>
    <p>XML Basic User from module security</p>
  </blockquote>
  
  <pre><code>&lt;record id="basic_user" model="res.groups"&gt;
      &lt;field name="name"&gt;Base User&lt;/field&gt;
          &lt;field name="implied_ids" eval="[(4, ref('base.group_user'))]"/&gt;
     &lt;/record&gt;
  </code></pre>
  
  <p>that give me an error : </p>
  
  <blockquote>
    <p>NameError: self is not defined</p>
  </blockquote>
  
  <p>My question is how to pass a default value to One2many relation using this xml definition, I don't want pass it throught field declaration in py. Thanks.</p>