public POIXMLProperties.CustomProperties getCustomProperties() {
        return this.properties.getCustomProperties();
    }
Currently, mostly a pass-through class to hold pkg and properties
and keep the general framework similar to our other POI-integrated
extractors.
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-microsoft-module/src/main/java/org/apache/tika/parser/microsoft/ooxml/xps/XPSTextExtractor.java