Hints to extend ogc-schemas for ISO 19139 gfc (feature catalogue)

Hello, thank you so much for this great library! I'm currently using it for parsing ISO 19139 XML, and it works great. In addition to the ISO 19139 schemas approved by OGC, i've the need to parse ISO 19139 representation of Feature Catalogue (ISO 19110). Although it's not part of the official schemas endorsed by OGC, i'm wondering if you could provide me hints how i could extend ogc-schemas to support in the same way the ISO 19139 gfc.xsd schema (http://www.isotc211.org/2005/gfc/gfc.xsd)?

Many thanks in advance for your support