title: Changing serializer fields on the fly
body: <p>For example I have the following serializer:</p>
  
  <pre><code>class UserSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = User
          fields = (
              'userid',
              'password'
          )
  </code></pre>
  
  <p>But I don't want to output password on GET (there are other fields in my real example of course). How can I do that without writing other serializer? Change the field list on the fly. Is there any way to do that?</p>