title: Django REST framework tuple being interpreted as a string?
body: <p>I've created the following serializer:</p>
  
  <pre><code>class KeywordSerializer(serializers.HyperlinkedModelSerializer):      
  
      class Meta:                                                                    
          model = Keyword                                                            
          fields = ('my_field')
  </code></pre>
  
  <p>However, when I try to use it in a viewset, I get the following error:</p>
  
  <blockquote>
    <p>The <code>fields</code> option must be a list or tuple or "__all__". Got str.</p>
  </blockquote>
  
  <p>But the issue is, fields is a tuple. I've even tried setting it to <strong>all</strong> or a list, but I get the same error. The same error occurs regardless of the name of the field.</p>
  
  <p>Would anyone know why this happens?</p>