title: Is it posible to get a model's unicode from another model?
body: <p>I have two tables, <code>Housing</code> and <code>Photo</code> (one to many relationship).
  The housing table returns unicode depending on type and transaction fields. I want the <code>Photo</code> unicode to be the <code>Housing</code>'s unicode + it's own primary key. Is this possible?</p>
  
  <pre><code>class Housing(models.Model):
      type = models.CharField(max_length=16)
      transaction = models.CharField(max_length=16)
  
  
      def __unicode__(self):
          if self.type.lower() == "house" and self.transaction.lower() == "sell":
              return "HS" + str(self.pk+100)
          elif self.type.lower() == "house" and self.transaction.lower() == "rent":
              return "HR" + str(self.pk+100)
          elif self.type.lower() == "apt" and self.transaction.lower() == "sell":
              return "AS" + str(self.pk+100)
          elif self.type.lower() == "apt" and self.transaction.lower() == "rent":
              return "AR" + str(self.pk+100)
          else:
              return "ERROR" + str(self.pk+100)
  
  class Photos(models.Model):
      housing= models.ForeignKey(Housing)
      photo_url = models.ImageField(upload_to="photos/", blank=True, null=True)
  
      def __unicode__(self):
          return "Img " + str(self.pk)
  </code></pre>