return builder;
        };

        // Test with JSON
        OutputStream jsonOutput = SearchEngineUtil.getXContentBuilderOutputStream(callback, XContentType.JSON);
        assertNotNull(jsonOutput);

        // Test with YAML
        OutputStream yamlOutput = SearchEngineUtil.getXContentBuilderOutputStream(callback, XContentType.YAML);
        assertNotNull(yamlOutput);
    }

    @Test