title: DRF serialisation issue: combining django-simple-history and django-polymorphic
body: <p>I am using regular Django models but have now started to incorporate a polymorphic model into my DRF REST API project using <code>django-polymorphic</code> and <code>rest-polymorphic</code>. I am also using <code>django-simple-history</code> to track changes to entries in my database. This all works fine for normal models and polymorphic models without a <code>HistoricalRecords()</code> field, but errors when trying to interact with any polymorphic model that has a <code>HistoricalRecords()</code> field:</p>
  
  <pre><code>django.core.exceptions.FieldError: Cannot resolve keyword 'material_ptr_id' into field.
  </code></pre>
  
  <p>In my serialiser for the polymorphic models, I use the following technique to serialise the <code>history</code> field:</p>
  
  <pre class="lang-py prettyprint-override"><code>class HistoricalRecordField(serializers.ListField):
      child = serializers.DictField()
  
      def to_representation(self, data):
          return super().to_representation(data.values())
  
  
  class ItemSerializer(serializers.ModelSerializer):
      history = HistoricalRecordField(read_only=True)
  
      class Meta:
          model = Item
          fields = ('history')
  </code></pre>
  
  <p>Is there a way to exclude the <code>material_ptr_id</code> field from being taken into account by the serialiser as it is not part of the parent model but only the child models? Or are there any obvious other mistakes I am making? Thanks for any help with this.</p>