Signature detection does not work

[reu24]

Signature fields aren't recognized - even in the test document provided in this repo.

What I've tried:
I ran commonforms on tests/resources/input.pdf with the option: --use-signature-fields. However it didn't not detect any signature fields.
When I lowered the confidence it detected the signature fields as text fields which is also incorrect.

Steps to reproduce:

• Install commonforms using uv pip install commonforms
• Download https://github.com/jbarrow/commonforms/blob/main/tests/resources/input.pdf
• Run commonforms input.pdf output.pdf --use-signature-fields
• Verify using e.g. Acrobat or pypdf that there aren't any signature fields in the PDF.

I looked into inference.py#prepare_form and it seems to be a problem with the detector.