title: Foreign key value is returning as an object instead of id in datatables in django
body: <p>When i try to get the data from the database I'm getting foreign key value as object instead of value.</p>
  
  <p>in Models.py</p>
  
  <pre><code>class UP_ROLE_MENU_MAP(models.Model):
      iRMID = models.AutoField(primary_key=True)
      iRoleID = models.ForeignKey(UP_ROLE_MASTER,on_delete=models.CASCADE,default='',db_column='iRoleID')
      iMenuID = models.ForeignKey(up_menus,on_delete=models.CASCADE,default='',db_column='iMenuID')
      iStatus = models.PositiveSmallIntegerField(default=1, blank=True,null=True)
  </code></pre>
  
  <p>In Views for DataTables</p>
  
  <pre><code>class OrderListJson(BaseDatatableView):
      model = UP_ROLE_MENU_MAP
      columns = ['iMenuID', 'iDeleteAccess','iAddAccess','iViewAccess']
      order_columns = ['iMenuID', 'iDeleteAccess','iAddAccess','iViewAccess']
      max_display_length = 10
      def render_column(self, row, column):
          if column == 'iViewAccess':
              return ...
          else:
              return super(OrderListJson, self).render_column(row, column)
  </code></pre>
  
  <p>output: ["up_menus object (3)", "0", "1", "link"]
  How can i get the value instead of object.</p>