title: How to get parent id
body: <p>I want to recuper contrat_parent_id in model 'facturation.lot' for filtring.</p>
  
  <p>Models :</p>
  
  <pre class="lang-python prettyprint-override"><code>class Contrat(models.Model):
      _name = 'facturation.contrat'
  
      code = fields.Char(string='Numéro Contrat', required=True)
      contrat_parent_id = fields.Many2one('facturation.contrat', string='Numéro Contrat Client')
  
  
  class Lot(models.Model):
      _name = 'facturation.lot'
      _description = 'Lots'
  
      contrat_id = fields.Many2one('facturation.contrat', ondelete='cascade')
      articlecontrat_ids = fields.Many2many('facturation.articleouvrage',string='Article Lot')
  
  class ArticleOuvrage(models.Model):
      _name = 'facturation.articleouvrage'
      _description = 'Ligne Articles'
  
      article_id = fields.Many2one('facturation.article',string='Article')
      ouvrage_id = fields.Many2one('facturation.ouvrage',string="Ouvrage")
  </code></pre>
  
  <p>View : </p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;record id="lot_view_form" model="ir.ui.view"&gt;
     &lt;field name="name"&gt;facturation.lot.form&lt;/field&gt;
     &lt;field name="model"&gt;facturation.lot&lt;/field&gt;
     &lt;field name="arch" type="xml"&gt;
         &lt;form&gt;
             &lt;sheet&gt;
                 &lt;field name="lib_lot" string="Lot"/&gt;
                 &lt;field name="contrat_id" options="{'no_create':True}"&gt;&lt;/field&gt;
                 &lt;notebook&gt;
                     &lt;page string="Composants" &gt;
                         &lt;field name="articlecontrat_ids" domain="[('ouvrage_id.contrat_id.id','=',1)]" options="{'no_create':True}" &gt;
                             &lt;tree&gt;
  </code></pre>
  
  <p>I want to recuper contrat_parent_id in model 'facturation.lot' for filtring.
  thanks</p>