How to override toc2map for ditamap generation with attributes?

[Poorva-25pxJS]

AEM Instance:
AEM 6.5 + SP7 + SP8 + XML Add On v3.8

Query:
We have a requirement to get the additional attributes (format, topic, chunk) added to the auto generated ditamap (from an uploaded index.html). While I was able to get these to reflect by making changes directly to /etc/fmdita/html2dita/toc2map.xsl. 

What would be the right approach to override this file? I tried an override at  /apps/fmdita/config/html2dita/toc2map_extended.xsl but that didn't quite work. 

[DivrajSingh]

The file toc2map.xsl is not extensible as of today.

If you intend to add same attribute values to the generated ditamap you may want to do this via post conversion event handler - you can refer to section "Conversion process event handler" of the API guide  (page 41)