title: django rest framework serializing a model to return its str representation
body: <p>Say that my serializer looks like so</p>
  
  <pre><code>class EntitySerializer(serializers.ModelSerializer):
      entity_instance = EntityInstanceSerializer(many=True)
      tags = EntityTagSerializer(many=True)
  
      class Meta:
          model = Entity
          fields = ('id', 'entity_instance', 'tags', 'note', 'source')
  
  class EntityTagSerializer(serializers.ModelSerializer):
      class Meta:
          model = EntityTagLabel
          fields = ('entity_tag_label',)
  </code></pre>
  
  <p>My tags model looks like this:</p>
  
  <pre><code>class EntityTag(models.Model):
      entity_tag_label = models.CharField(max_length=255, unique=True)
  
      def __str__(self):
          return self.entity_tag_label
  </code></pre>
  
  <p>Now this is fine and all, but my response looks like this:</p>
  
  <pre><code>   ...
          "tags": [
              {
                  "entity_tag_label": "SENDER"
              }
          ],
  </code></pre>
  
  <p>Is it possible for my tags serializer to simply return the string representation of each tag? That way I would just have</p>
  
  <pre><code>        "tags": [
               "Sender",
          ],
  </code></pre>
  
  <p>as an example</p>