Get and Set unusal Metadata

[romanstark]

Dear Community

I do need to fill a FormField PDF/A template, which is regulated by German health care government. It is not allowed to change the template and reading the requirements, I noticed that I have to fill some unusual XMP metadata in the document. I could not find in the documentation, if there are methods to fill these meta data. As an example. There are 6 named meta data XPM "fields" like for example "Number_of_characters_first_name" in the template, I have to set prior saving the final PDF. Is there a way to do that? I've seen the setters and getters for common Meta-Data, but nothing for unusal ones.

Thank you,
Roman