def validate_templates(self, value): manager = TemplateManager(settings.RAFEE_REPO_DIR) bad_template_names = [] for template_name in value.split(","): if not manager.template_exists(template_name): bad_template_names.append(template_name) if len(bad_template_names) > 0: raise serializers.ValidationError(TEMPLATES_NOT_FOUND.format(bad_template_names)) return value