tags = models.Tag.objects.usage_for_model(models.Book, counts=True, extra={'where': [extra_where]})
fragment_tags = models.Tag.objects.usage_for_model(models.Fragment, counts=True,
extra={'where': ['catalogue_tag.category = "theme"'] + [extra_where]})
categories = split_tags(tags)
tags = models.Tag.objects.usage_for_model(models.Book, counts=True, extra={'where': [extra_where]})
fragment_tags = models.Tag.objects.usage_for_model(models.Fragment, counts=True,
extra={'where': ['catalogue_tag.category = "theme"'] + [extra_where]})
categories = split_tags(tags)