Returns a list of tuples. The first element in each
        tuple is the coded value for the option that will
        appear in the URL query. The second element is the
        human-readable name for the option that will appear
        in the right sidebar.

def lookups(self, request, model_admin):
        """
        Returns a list of tuples. The first element in each
        tuple is the coded value for the option that will
        appear in the URL query. The second element is the
        human-readable name for the option that will appear
        in the right sidebar.
        """

        output = []
        for i in models.Model.objects.values('information__type').distinct():
            ct = i['information__type']

            if ct is not None:
                ct = ContentType.objects.get(pk=ct)
                output.append([ct.pk, ct.app_label + '.' + ct.model])

        return output