title: Attribute error when attempting to get a value for field
body: <p>I'm working with the django rest framework and the serializer I'm trying to use is creating errors. I'm trying to do something like <a href="https://gist.github.com/anonymous/7463dce5b0bfcf9b6767" rel="noreferrer">https://gist.github.com/anonymous/7463dce5b0bfcf9b6767</a> but I still get the error. the models are </p>
  
  <pre><code>class Visitor(models.Model):
  
  user = models.OneToOneField(User)
  check_ins = models.IntegerField(default=0)
  
  @classmethod
  def create(cls, username, email, password):
      user = User.objects.create_user(username, email, password)
      visitor = cls(user=user)
      visitor.save()
      return visitor
  
  def __str__(self):
      return self.user.username
  </code></pre>
  
  <p>and the default user class and the serializers are</p>
  
  <pre><code>class UserSerializer(serializers.ModelSerializer):
      class Meta:
          model=User
          fields = ('username')
  
  class VisitorSerializer(serializers.ModelSerializer):
      user = UserSerializer()
  
      class Meta:
          model=Visitor
          fields = ('id','check_ins','user')
  </code></pre>
  
  <p>I get this error</p>
  
  <p>Got AttributeError when attempting to get a value for field <code>user</code> on serializer <code>VisitorSerializer</code>.
  The serializer field might be named incorrectly and not match any attribute or key on the <code>QuerySet</code> instance.
  Original exception text was: 'QuerySet' object has no attribute 'user'.</p>