Update existing tiff: add new tag

[carlos-vl]

Hello, I would like to use pylibtiff to add tags to existing tiffs programmatically.
I have some multipage tiff, and I would like to add a tag "TIFFTAG_SUBFILETYPE" to some of the pages.
However, I do not want to have to write the whole tiffs again, as they are very large file.
Can I do this with pylibtiff?

Thanks!

[carlos-vl]

I managed to do this using tiffset instead