title: django_countries in django rest framework
body: <p>I am trying to create an API which can return all the countries using django_countries.</p>
  
  <p>I am trying something following but it is not working. As an individual field, it works fine but with complete countries list it is giving an error.</p>
  
  <pre><code>from django_countries import countries
  
  
  class CountrySerializer(serializers.Serializer):
  
      country = serializers.ListField(source=countries)
      class Meta:
      fields = ("country",)
  </code></pre>